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S0022407320304878
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In a recent paper devoted to the study of longitudinal optical forces exerted by off axis Bessel beams in the Rayleigh regime in generalized Lorenz Mie theory new kind of optical forces are discovered . They are different than the well established scattering and gradient forces and called axicon forces . In the present paper within the same framework we demonstrate the existence of a new kind of axicon terms associated with gradient forces which are zero both when the axicon angle is zero and when an on axis configuration is considered .
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Longitudinal gradient optical forces of off axis Bessel beams are investigated. Axicon terms associated with these forces are uncovered. These terms are zero when the axicon angle is zero. They are zero as well for on axis configurations.
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S0022407320304994
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An automated spectral fitting algorithm designed for the extraction of temperature information from experimental NO LIF spectra is presented and analysed . With the aid of the Thermo NO LIF the high accuracy of multi line NO LIF thermometry are demonstrated in the burnt gases region of a near adiabatic Bunsen type premixed flame . The results are compared with the temperature measured using N
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A novel program designed to determine the temperature from excitation spectra of NO LIF is publicly available. The multi line NO LIF thermometry can achieve an accuracy of 0.5 . Uncertainty can arise from using a narrowband laser under low pressures where the spectral linewidth is too narrow. Thermo NO LIF is available at http pc2a.univ lille.fr fr thermo no lif.
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S0022407320305021
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In our previous publications we have presented revised and extended versions of Hottels total emissivity charts for water vapor carbon dioxide carbon monoxide and their mixtures . In applications not only emissivity but also absorptivity is required . In 1935 Hottel and Mangelsdorf produced formulae for calculating total absorptivity using total emissivity for carbon dioxide and water vapor . In 1959 Penner proposed another formula . In this paper we determine accuracy of these approximate formulae using the most advanced line by line model based on HITEMP 2010 . The accuracy has been determined over 4003000K range for both absorbing gas temperatures and source temperatures for total pressure range from 0.5bar to 80bar and mole fractions from 0.1 to 1.0 for carbon dioxide water vapor and carbon monoxide . The path length range examined is from 0.01 to 3000barcm . Furthermore new formulae have been derived and they provide more accurate predictions .
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Procedure for calculating gray gas absorptivities from gas emissivities. Error assessment for Hottels and Penners scaling rules. New more accurate correlations. The new formulae lead to absorptivities within 5 margin on average.
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S0022407320305057
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In this work the scattering absorption and the far field thermal emission properties of clusters of randomly distributed magneto optical nanoparticles are studied considering spectral directional and polarization state of the electromagnetic waves . We observe the Zeeman splitting effect in the scattered absorbed and far field emitted energy the magnitude of which are directly influenced by the multiple scattering effect among the nanoparticles . The scattering and thermally emitted waves by the cluster have large degrees of circular polarization in directions parallel to the applied magnetic field
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Electromagnetic scattering absorption and thermal emission of clusters of randomly distributed magneto optical nanoparticles are investigated for the dynamical tuning of the apparent radiative properties of magneto optical particle dispersed system. The spectral directional and polarized multiple scattering and thermal emission of the magneto optical nanoparticle clusters are studied. The multiple scattering effect is studied. The reciprocity of all the four Stokes parameters can be broken in the multiple scattering of magneto optical nanoparticle clusters.
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S0022407320305100
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The Atmospheric Chemistry Experiment Fourier transform spectrometer has been measuring water vapor and methane in the stratosphere and mesosphere from low Earth orbit since 2004 . Recently substantial increases in water vapor in the upper atmosphere were observed with the MLS and SABER satellite instruments . The main source of water vapor in the upper atmosphere is methane oxidation . ACE FTS data show substantial water and methane increases and confirm that the methane increases are too small to explain the water increases . Therefore changes in the transport of water across the tropical tropopause layer and in atmospheric dynamics are responsible for the positive water trends .
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Average altitude latitude distributions of H. O CH. and potential water volume mixing ratios from ACE mission. Trends and solar responses of H. O CH. and potential water volume mixing ratios from ACE mission. O volume mixing ratio time series for stratosphere and mesosphere.
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S0022407320305112
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Fast accurate and stable computation of the Clebsch Gordan coefficients is always desirable for example in light scattering simulations the translation of the multipole fields quantum physics and chemistry . Current recursive methods for computing the C G coefficients are often unstable for large quantum numbers due to numerical overflow or underflow . In this paper we present an improved method called the sign exponent recurrence for the recursive computation of C G coefficients . The result shows that the proposed method can significantly improve the stability of the computation without losing its efficiency producing accurate values for the C G coefficients even with very large quantum numbers .
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The sign exponent recurrence method is presented as an improved recursion method for computing Clebsch Gordan Coefficients. The sign exponent recurrence method is more stable than the widely applied three term linear recurrence method while having the same level of accuracy and efficiency. The accuracy and efficiency are demonstrated by comparing with Python library SymPy.
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S0022407320305124
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In this paper we theoretically investigate the spectroscopic properties of a simple hybrid metasurface consisting in a periodic array of a Si Au pattern in the mid infrared spectral region . Our simulations show that our hybrid metasurface exhibits a strong spectral absorption band in the
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Design and spectral investigations on a hybrid metasurface based on a Si Au and a rod ring architecture. Absorption peak observed in the mid infrared region for the hybrid shows a completely different behavior than that of the Au Au counterpart. Resonance is obtained for a wavelength to cell dimension ratio of 1.5 lower than the typical threshold. Resonance frequency of the surface can be tuned as a function of rod dimensions. Thermal deposition in the structure reveals superior qualities for the hybrid cell by comparison to the full metallic counterpart.
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S0022407320305148
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We numerically simulate multiple light scattering in discrete disordered media represented by large clusters of irregular non absorbing particles . The packing density of clusters is 0.5 . With such conditions diffuse scattering is significantly reduced and light transport follows propagation channels that are determined by the particle size and topology of the medium . This kind of localization produces coherent backscattering intensity surge and enhanced negative polarization branch if compared to lower density samples .
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Light transport in dense clusters of particles is highly localized in the propagation channels determined by the particle size and topology of the medium. Light localization produces an intensity surge and enhanced negative polarization branch at backscattering if compared to low density samples. The negative polarization near backscattering apparently originates from single scattering by particles in the surface layer. Clusters of particles with the same packing density but topologically distinct may have different backscattering properties.
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S0022407320305173
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Laser powder bed processing is widely employed in 3D printing . The technological processes strongly depend on such effective radiative transfer properties of powder beds as the absorptance and the radiation penetration depth . However it is still not completely clear what are the principal factors influencing these properties and what are the possible ranges of their variation . For theoretical investigation of the radiative transfer a ray tracing method is developed where the effective properties of powder beds are expanded in series of the reflectance of the solid phase surface . Once the coefficients of the power series are calculated they can be used for any combination wavelength material thus facilitating parametric analysis . Powder beds are modeled by equal spheres packed in regular cubic symmetry structures of various density . The calculated radiation penetration depth can vary from few particle diameters for close packed structures with moderate solid phase absorptance to few tens of particle diameters for less dense power beds of a highly reflecting material . The effective absorptance of the powder bed is revealed to decrease significantly with the packing density . The calculated dependence of the powder bed absorptance versus the solid phase absorptance and the density is validated by the known experimental data . The calculated angular distribution of the radiation reflected by a powder bed slightly deviates from the cosine like distribution corresponding to the diffuse reflection law . It is validated by the known experimental data . A modified model of equivalent medium is proposed to approximate the obtained ray tracing results by analytic expressions .
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Metal powder beds are modeled by equal spheres packed in regular cubic symmetry structures. Radiative properties are expanded in power series of the opaque phase reflectance with coefficients calculated by ray tracing. The calculated absorptance and reflectance are sensitive to the structure orientation and density and agree with experiments. Radiation can penetrate into powder beds to the depth from few to few tens particle diameters. The proposed modified model of equivalent medium approximates the obtained ray tracing results.
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S0022407320305197
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Earth s atmosphere contains interplanetary dust particles which are a key ingredient to understand planetary phenomena yet the study of their physicochemical properties without external interferences at the single particle level is limited . With the optical trapping technique a single dust particle can be stably trapped in air for subsequent characterization . We report on measurements of the single particle extinction of trapped particles using cavity ringdown spectroscopy at ultraviolet wavelength around 308nm . We also present Raman spectral features of chemical groups in individually trapped particles . Two simulants of extraterrestrial materials along with carbon spheres and volcanic ashes were trapped and spectroscopically characterized . In addition to the on trap measurements the particles morphological and mineralogical information was obtained from off trap measurements using scanning electron microscopy and energy dispersive spectroscopy . This study demonstrates that the integration of OT with cavity ringdown and Raman spectroscopy provides a new tool to gain multimodal information on the physicochemical properties of single IDPs with minimum to no external interferences .
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Single particle extinctions of single trapped extraterrestrial dust particles were measured using cavity ringdown spectroscopy. Raman spectral features of chemical groups in individually trapped particles were characterized. Demonstrated optical trapping cavity ringdown spectroscopy and optical trapping Raman spectroscopy techniques for extraterrestrial dust particles.
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S0022407320305215
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For the first time herein we report the theoretical investigation on short and elongated photonic nanojets generated by single solid hollow core shell microparticles illuminated with focused Gaussian beams . This investigation is carried out using developed analytical equations based on Bromwich formalism . The effect of the beam waist thickness of shell size and refractive index of the microparticle on the characteristic parameters of the PNJs such as maximum electric field enhancement spatial separation between the PNJs and length of the PNJs is studied in detail . The electric field enhancement values of the PNJs upon FGB illumination are compared to those obtained from the plane wave illumination .
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Using developed analytical equations for the first time the theoretical investigation has been done on short and elongated photonic nanojets PNJs generated by single solid hollow core shell microparticles illuminated with focused Gaussian beams FGBs . The effect of the beam waist thickness of shell size and refractive index of the microparticle on the characteristic parameters of the PNJs has been studied systematically. The electric field enhancement values of the PNJs upon FGB illumination are compared to those obtained from the plane wave illumination. We strongly believe that the analytical equations reported in this manuscript will be useful to the Nanophotonics community to understand the characteristic parameters of the PNJs generated by various types of solid hollow core shell microparticles of any arbitrary size illuminated by FGBs with different beam waists.
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S0022407320305306
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Cyanoacetylene the simplest cyanopolyyne is an abundant interstellar molecule commonly observed in a vast variety of astronomical sources . Despite its importance as a potential tracer of the evolution of star forming processes the deuterated form of cyanoacetylene is less observed and less studied in the laboratory than the main isotopologue . Here we report the most extensive spectroscopic characterization of DC
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Combined rotational and ro vibrational analysis of DC. High resolution infrared spectra. Rotational spectra in 14 vibrational excited states. Anharmonic resonances network. Line catalog for astronomical applications.
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S0022407320305379
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Based on the generalized Lorenz Mie theory and the angular spectrum decomposition method we calculate the time averaged optical torque exerted on an absorptive dielectric sphere of arbitrary size illuminated by a TM polarized Airy light sheet and the negative optical torque is particularly emphasized . The influence of the transverse scale parameter
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Optical torque exerted on an absorptive dielectric sphere of arbitrary size illuminated by a polarized Airy light sheet is investigated using GLMT. The negative optical torque is particularly emphasized. The influence of the transverse scale parameter. and attenuation parameter. of the Airy light sheet on the torque is discussed.
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S0022407320305392
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S and electronic states of strontium sulfide are characterized at the CASSCF MRCI Q level of theory . This is the first work to provide a reliable picture of the potential energy curves showing the challenges one might face to investigate them either theoretically or experimentally . Spectroscopic parameters and averaged dipole moment functions are reported . Einstein emission coefficients provide relevant information on the relative intensities for selected transitions . Radiative lifetimes are also estimated and an accurate value of dissociation energy for the ground state obtained . Perturbing states in the
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Reliable and accurate potential energy curves for S and states of SrS. Most complete characterization of the states to date. Transition moments Einstein A. emission coefficients and radiative lifetimes. Identifies transitions most likely to be investigated experimentally.
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S0022407320305409
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Unlike standard dielectric materials the interaction of light sheets of arbitrary wavefronts with a particle exhibiting circular dichroism such as chiral topological insulator liquid crystal or metamaterials to name a few examples requires additional fundamental developments from the standpoint of scattering radiation force and torque theories.The purpose of this work is therefore directed toward developing an exact analytical formalism applicable to a 2D object exhibiting TM TE mode conversion and possessing an arbitrary geometrical cross section . Exact mathematical expressions for the longitudinal and transverse optical radiation force and axial torque components are derived stemming from series expansions for the incident and scattered electromagnetic fields using the mode matching method in cylindrical coordinates . The generalized radiation force and torque expressions depend on the beam shape coefficients of the incident light sheet and the scattering coefficients of the object . Extra new terms describing the generation of the scattered cross polarized waves induced due to TM TE mode conversion contribute to the radiation force and torque series . Numerical illustrative examples for a circular lossy electromagnetic conductor cylinder are provided assuming illumination by various wavefronts ranging from plane progressive standing and quasi standing waves to other non paraxial Airy light sheets with linear and circular polarization . In essence the present theoretical formalism provides a complete analysis in the framework of the generalized LorenzMie theory in 2D for any particle exhibiting circular dichroism in any structured light sheet . Potential applications are in the design optimization and the numerical predictions and computation of the optical radiation force and torque for particle transport and rotation in the realm of optical tweezers particle manipulation and stabilization . Some perspectives are discussed and replies to misleading comments made in the literature on the publication given by Ref .
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Arbitrary shaped light sheets are considered on a particle exhibiting circular dichroism. Generalized radiation force and torque expressions are derived accounting for TM TE mode conversion. Computations illustrate the analysis with particular emphasis on polarization and light sheet properties. The radiation force and torque components take negative positive or neutral values. The results can be used as. information in research related to the study of the mechanical effects of light matter interactions.
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S0022407320305458
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We present an algorithm and FORTRAN codes to compute the opposition effects in the reflection of light from a semi infinite discrete random medium at normal incidence to the boundary of the medium . It is assumed that the medium is sparse enough that the waves propagating between the scatterers are spherical . In this case the reflection matrix is determined only by contributions of the incoherent and coherent components . When calculating the coherent component the contribution of the doubly scattered radiation to the reflection matrix is rigorously taken into account while the contributions of the higher orders are calculated approximately . To be more specific the multiply scattered radiation coming to some point of the medium from above is calculated exactly but the radiation coming from below approximately . Under this supposition the solution of the system of integral equations is reduced to that of the system of linear algebraic equations . The matrix of this system is calculated with the recurrent relation which radically speeds up the computations as compared to the direct procedure . This allows the opposition effect characteristics to be computed rapidly enough so that the codes may be used in interpretation of the remotely measured intensity and polarization of light reflected by different media to estimate at least at a qualitative level their properties .
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A fast algorithm to calculate the opposition effects is presented. FORTRAN codes to compute the opposition effects are described. Errors introduced by the algorithm are concisely considered.
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S0022407320305586
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Estimates of atmospheric carbon dioxide concentration from satellites now span multiple years and are providing information on key processes in the carbon cycle . Methodology for retrieving CO
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Uncertainties in trace gas spectroscopy impact bias and variance of satellite retrievals of carbon dioxide. Linear error analysis propagates parameter uncertainty to error estimates for retrieved quantities. Spectroscopic model choices for O2 and CO2 result in XCO2 error estimates that vary in space and time. Errors in laboratory conditions result in nearly constant XCO2 error estimates.
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S0022407320305616
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This work extends the scope of the previous study on the electromagnetic radiation force on a perfect electromagnetic conductor cylinder F.G. Mitri J. Quant . Spectr . Rad . Transfer
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The electromagnetic radiation force on a perfect electromagnetic conductor PEMC sphere is considered. A linearly polarized plane wave illuminates the PEMC sphere. The force is not affected by the admittance of the PEMC sphere material. Scattering asymmetry parameters for the co polarized and cross polarized waves are derived and computed. The results are important from the standpoint of the basics of the electromagnetic radiation force theory.
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S0022407320305732
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The results of theoretical calculations for the ground and excited levels of the iridium neutral atom and its negative ion are presented and the corresponding photodetachment energies . Calculations were carried out with the four component multiconfiguration Dirac Hartree Fock method and with the spin free relativistic second and eight order Douglas Kroll Hess method and the infinite order two component method and high level correlated methods . The spin orbit coupling is introduced via the restricted active space state interaction method with the use of the atomic mean field SO integrals . The results are compared and interpreted in comparison with the experimental results . The theoretical analysis suggest different assignment and interpretation of atomic and anionic levels and existence of several anionic bound states . A comparative analysis of the accuracy of two component methods is also presented .
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Theoretical description of the energy levels of neutral iridium and its negative ion. Four component multiconfiguration Dirac Hartree Fock method. The spin free relativistic second and eight order Douglas Kroll Hess method. The infinite order two component method and high level correlated methods. Different theoretical assignment and interpretation of atomic and anionic states.
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S002240732030580X
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Excitation energies wavelengths transition probabilities weighted oscillator strengths and line strengths for electric dipole magnetic dipole electric quadrupole and magnetic quadrupole transitions between the states of the 2
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Excitation energies and lifetimes for the lowest 236 fine structure levels of Zr XXXV are calculated. Wavelengths transition rates weighted oscillator strengths and line strengths for E1 M1 E2 and M2 transitions of Zr XXXV are calculated. The calculations are performed using the fully relativistic multiconfiguration Dirac Hartree Fock MCDHF method. The present MCDHF energies wavelengths and electric dipole oscillator strengths are compared with other available theoretical results.
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S0022407320305811
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In the analysis of light scattering by small particles the Generalized Lorenz Mie Theory describes the incident beam with a set of Beam Shape Coefficients that can be calculated with three different approaches viz . quadratures finite series and localized approximations . Choosing between them may not be self evident . A Bessel Gauss beam is a finite energy physically realizable wave field resulting from the apodization of a Bessel beam by a Gaussian function . This paper provides a comparison between the aforementioned techniques for the evaluation of the BSCs of scalar BGBs with distinct axicon angles and confinement parameters including field reconstructions . All three methods agree quite well in the paraxial regime although as the axicon angle or the topological charge increases differences in the BSCs for each method become more and more evident .
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Scalar Bessel Gauss beams are described in the generalized Lorenz Mie theory GLMT . Beam shape coefficients are calculated using three remodeling techniques. Quadratures finite series and localized approximations are compared for distinct topological charges and axicon angles. Examples of calculations of beam shape coefficients and remodeling of radial electric field component are presented. This work is an important contribution to the field and may also bring greater interest to the use of the finite series method to compute beam shape coefficients.
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S0022407320305847
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The relativistic hyperfine constants of the heavy inert gas element xenon 131 isotope have been calculated . The calculations executed through the Multiconfiguration Dirac Hartree Fock method yield the hyperfine constants of 128 levels belonging to the n
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The interaction between the nucleus of xenon 131 isotop and the orbit electrons is studied. As a result of this study the hyperfine constants of 128 levels belonging to the n. n 6 7 8 9. n 4 5 6 n. n 5 6 7 8 n. n 6 7 8 and 5g. intermediate Rydberg series are provided. The magnetic and electric field gradients at the nucleus site are extracted by combining the previous results with experimental values of the nuclear magnetic dipole and electric quadrupole moments of the atom under consideration. The Multiconfiguration Dirac Hartree Fock MCDHF method is employed.
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S0022407320305859
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After several decades development of retrieval techniques in aerosol remote sensing no fast and accurate analytical Radiative Transfer Model has been developed and applied to create global aerosol products for non polarimetric instruments such as Ocean and Land Colour Instrument Sentinel 3 and Meteosat Second Generation Spinning Enhanced Visible and Infrared Imager . Global aerosol retrieval algorithms are typically based on a Look UpTable technique requiring high performance computers . The current eXtensible Bremen Aerosol cloud and surfacE parameters Retrieval algorithm also utilizes the LUT method . In order to have a near real time retrieval and achieve a quick and accurate FIRST LOOK aerosol product without high demand of computing resource we have developed a Fast and Accurate Semi analytical Model of Atmosphere surface Reflectance for aerosol remote sensing . The FASMAR is developed based on a successive order of scattering technique . In FASMAR the first three orders of scattering are calculated exactly . The contribution of higher orders of scattering is estimated using an extrapolation technique and an additional correction function . The evaluation of FASMAR has been performed by comparing with radiative transfer model SCIATRAN for all typical observation illumination geometries surface aerosol conditions and wavelengths 412 550 670 870 1600 2100nm used for aerosol remote sensing . The selected observation illumination conditions are based on the observations from both geostationary satellite and polar orbit satellite . The percentage error of the top of atmosphere reflectance calculated by FASMAR is within 3 for typical polar orbit geostationary satellites observation illumination geometries . The accuracy decreases for solar and viewing zenith angles larger than 70
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A fast radiative transfer model FASMAR for aerosol remote sensing was developed. The accuracy of FASMAR is better than 3 for GEO and LEO satellite observations. FASMAR is valid for all surface and atmospheric conditions. FASMAR is used to create NRT FIRSTLOOK global aerosol products.
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S0022407320305860
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For decades now the retrieval of aerosol property has been successfully achieved from space borne sensors from which measurements it is possible to derive specific parameters such as optical thickness absorption type refractive index or size distribution . In the reflective spectral domain remote sensing of aerosol properties relies on the top of atmosphere measurement of the sun irradiance scattered by aerosols in different directions . This measure is intrinsically linked to the aerosol phase function . Ground based measurements are made for many viewing directions providing a good description of this phase function . For satellite remote sensing the phase function can not be measured in so much detail . Only a single scattering angle for mono viewing sensors or a limited range for multi view sensors is accessible . The associated geometry varies very significantly along the swath from East to West and along the orbit from North to Tropics and South . Whatever the considered aerosol retrieval approach the performance can not be the same from these very different geometrical configurations and may significantly differ . This aspect is in general not well documented . In this paper the scattering angle range distribution is described in the case of the EPS SG 3MI multi view polarimeter . Based on reference aerosol phase functions it is anticipated how the retrieval performance could be impacted . Other cases are simulated trying to extrapolate the conclusion to other types of sensors having more limited swath or number of views . The ScARD is described for these different situations including the variation along the orbit and along the swath . Important recommendations are drawn including the need to document the geometrical part of the information content provided by the sensor to better consider the associated classes of viewing geometry for the development of retrieval algorithms but also for the validation of products .
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How aerosol retrieval is influenced by the geometry. Definition of the scattering angle range distribution. Typical information content for some earth observing sensors. Recommendation for the development of aerosol retrieval and products.
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S0022407320305884
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The helium singlet 1s4d 1s2p line has been measured in a corona discharge done in liquid helium at 4.2K . A significant shift towards the blue direction is visible on the spectrum . Using an empirical model for the He He potential energy difference we have performed a fitting of the line shape . The best fit result is in good agreement with the experimental spectrum . It is shown that the blue shift is determined by the maximum of the potential energy difference function . Based on the fitting results we give an estimate of this quantity .
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Corona discharges in liquid helium have indicated the presence of strong blue shift on the 492.2nm atomic line. Using an empirical model for the He He potential energy difference we have performed a fitting of the line shape. Qualitative and quantitative properties of the energy difference are inferred based on the best fit result.
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S0022407320305914
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Turbulence induced wavefront deformations cause the irradiance of an optical signal to fluctuate resulting a in serious degradation in the bit error rate performance of optical wireless communication system . Adaptive optics is an effective technique to compensate for the wavefront aberrations to reduce the fluctuations in the received intensity . In this paper we investigate how the adaptive optics technique affects the BER performance of an oceanic OWC system employing binary phase shift keying subcarrier intensity modulation and aperture averaging . To evaluate BER performance in weak oceanic turbulence the required entities such as the received optical power captured by a circular aperture and the aperture averaged scintillation index measuring the fluctuations in the received irradiance are derived . The effect of adaptive optics correction of various wavefront aberrations on the BER performance is illustrated and the performance of the adaptive optics OOWC system is compared to that of a non adaptive optics OOWC system by the metric defined .
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An OOWC system employing aperture averaging and Gaussian beam is considered. Binary phase shift keying subcarrier intensity modulation is used to modulate the Gaussian laser. Effects of adaptive optics on BER performance of the OOWC system operating in weak oceanic turbulence are investigated. BER performance of the OOWC system with adaptive optics is compared to that of the OOWC system without adaptive optics.
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S0022407320305938
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In this study the echo speckle characteristics of the Laguerre Gauss vortex beams scattered from random rough surface targets were examined based on the Rytov Approximation Theory . In addition the expressions of the intensity correlation and coherence functions along with the normalized intensity variances of the speckle fields were derived . The coherent lengths and scintillation indexes of the speckle fields were then numerically simulated and the speckle characteristics of the Laguerre Gauss vortex beam were compared with those of the Gaussian beams . The effects of the topological charges rough target radii initial beam radii turbulence intensities and roughness degrees of the targets on the speckle characteristics of the LG vortex beams were analyzed . This study s results showed that in the weak turbulence regions the target characteristics were the main influencing factors of the speckle fields . Meanwhile in the strong turbulence regions the turbulence effects were the main influencing factors of the speckle fields . The influence effects of turbulent atmosphere and target characteristics on the coherent lengths and scintillation effects of the vortex beam echoes were observed to be less than those of the Gaussian beams . In addition the influence effects of the turbulent atmosphere on coherent lengths and scintillation effects of the vortex beams echoes with small topology were found to be minimal . Therefore this study s results can potentially provide theoretical and technical guidance for the future applications of laser target detection target recognition and speckle measurement processes in space .
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The speckle carries a large amount of target information the target features can be obtained by measuring the speckle. There are few reports regarding the echo speckle characteristics of vortex beams currently. The echo speckle characteristics of the Laguerre Gauss LG vortex beams scattered from random rough targets were examined.
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S0022407320305975
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Photophoresis in the slip flow and free molecular regimes under plane wave illumination is investigated in terms of the asymmetry factor for non volatile homogeneous low loss spherical particles with an arbitrary index of refraction . An analytic and closed form expression for this important factor is derived which can be used to predict photophoretic forces exerted on microparticles of arbitrary size parameters therefore in any optical regime . Examples are given in terms of the behavior of both the asymmetry factor and the internal field distribution showing differences between photophoresis of dielectric negative index and magnetodielectric particles .
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Photophoresis for both slip flow and free molecular regimes is presented for arbitrary index microspheres. It uses the Mie theory for lossy and homogeneous spheres and extends previous analysis for dielectric scatterers. An analytic and closed form expression is derived for the asymmetry factor which can be used to predict photophoretic forces exerted on microparticles of arbitrary size parameters. Examples are given in terms of the behavior of both the asymmetry factor and the internal field distribution. Examples include dielectric negative index and magnetodielectric particles.
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S0022407320306063
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In this paper we present the vector radiative transfer theory for a discrete random medium illuminated by a Gaussian beam . The analysis is based on a plane wave spectrum representation for a Gaussian beam and uses an approach developed previously for a discrete random medium illuminated by a plane electromagnetic wave . Specifically we establish an integral representation for the coherent field define an approximate coherent field that satisfies the differential equation fulfilled by the coherent field corresponding to a plane electromagnetic wave and matches the Gaussian beam at the interface of the particulate medium and finally derive the vector radiative transfer equation . For weakly focused Gaussian beams the resulting equation is the traditional radiative transfer equation .
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Radiative transfer in discrete random media illuminated by a Gaussian beam. Coherent field. Vector radiative transfer equation. Numerical solution of the radiative transfer equation.
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S0022407320306087
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In this paper we present numerical methods for solving the phenomenological scalar radiative transfer equation for a discrete random medium illuminated by a Gaussian beam . These rely on the Fourier transform method for the horizontal variables and the discrete ordinate method with matrix exponential for solving the underlying one dimensional radiative transfer equation in the wavenumber domain . The problem of a Gaussian beam at oblique and normal incidence as well as the searchlight problem are treated . A complete description of the methods and the numerical algorithms is provided .
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Radiative transfer in discrete random media illuminated by a Gaussian beam. Coherent field. Vector radiative transfer equation. Numerical solution of the radiative transfer equation.
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S0022407320306166
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Laser plasmas produced by ablation of a gold target in a vacuum are spatially and temporally characterized by optical emission spectroscopy . A Nd YAG laser 1064nm pulse width 15ns and fluences of 5.8 and 11J cm
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Imaging spectroscopy of gold LPPs has been assessed. Fundamental plasma parameters were spatially and temporally quantified. Plasma temperature calculated comparing experimental and atomic Boltzmann LTE spectra. Ion abundance as a function of plasma temperature has been calculated. The dynamics of gold plasma species generated near ablation threshold is described.
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S002240732030618X
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The opacity information of a finite temperature plasma is an important property and requires the population distribution of a given plasma condition . A population kinetic code for plasma spectroscopy FLYCHK has been widely used by researchers to study the spectroscopic properties of high energy density plasmas under a wide range of conditions . In this study the FLYCHK calculation of the Planck and Rosseland mean opacities of low to high Z elements such as aluminum
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FLYCHK calculation on Planck and Rosseland mean opacities of Al Cu and Au in wide temperature density ranges is reported. Comparisons with opacities from PROPACEOS and ATOMIC code provides the validity range of FLYCHK opacity as well as its limitation. Correlation of the plasma coupling parameter with opacity and the sensitivity of LTE and NLTE conditions are reported. This investigation provide a deeper insight on the opacity related to plasma parameters and validity of FLYCHK opacity.
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S0022407320306464
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The discrete transfer method is adopted to solve the transient radiative transfer with collimated or diffuse irradiation in variable index media with arbitrary distribution of refractive index . The advantage of this approach is its ability to simulate the transient radiation in semi transparent media with non continuous refractive index distributions . The solution method is verified by comparison the results with those reported in literature for one two and three dimensional cases . The reflectance and transmittance for some locations over the boundaries are obtained and the effects of optical thickness scattering albedo and scattering phase function are examined .
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The transient radiative transfer in variable index media is solved by the discrete transfer method. The solution method is applicable for continuous or non continuous refractive index distributions. The method is adopted for one and multi dimensional media. The boundaries may be exposed to collimated irradiation. The reflectance and transmittance are reported for one and two dimensional media.
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S0022407320306592
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We present results of measurements of the oscillator strength of intercombination lines of He like Vanadium ions in high energy density laser produced plasmas and compare them with the simulations from commonly used codes and data from the NIST database . Whilst not yet sufficiently accurate to constrain different trusted atomic physics models for the particular system studied our results are in agreement with the available data within experimental error bars yet differ from cruder approximations of the oscillator strength used in certain atomic kinetics packages suggesting that this general method could be further extended to be used as a measurement of the oscillator strength of additional atomic transitions under the extreme conditions that are achieved in HED experiments .
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The ratio of an optically thick to an optically thin line can be used to measure the oscillator strength of the optically thin transition in cylindrical plasmas. We have obtained the first experimental results of this method for the intercombination line of the He. complex at the OMEGA 60 laser. The results agree with those from the NIST database showing the potential of this method to measure transition strengths.
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S0022407320306634
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In this study banded one gas spectral line based weighted sum of gray gases model is coupled with a 3 D radiation code based on method of lines solution of discrete ordinates method for freeboard of METU 0.3 MW
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Band wise selection of pathlengths for banded SLW 1 provides accurate predictions. Banded SLW 1 accurately predicts source terms and heat fluxes in air and oxy fired cases. Increasing particle load further improves the accuracy of banded SLW 1. Use of spectral emissivity is necessary for optically thin media bounded by hot walls. Accuracy of gray wall assumption depends on spectral properties of wall materials.
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S0022407320306701
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Black carbon aerosols exert important effects on regional and global climate whilst there still are significant uncertainties in their optical properties particularly the spectral varying Angstrom exponents . This study numerically evaluates the influences of coating morphologies on optical properties of BC with non absorbing coating and evaluates the sensitivity of their Angstrom exponents including extinction Angstrom exponent absorption Angstrom exponent and single scattering albedo Angstrom exponent to particle microphysics with the multiple sphere T matrix method . Among all microphysical parameters the shell core ratio and size distribution play substantial roles in determining the EAE AAE and SSAAE of coated BC wherein the dependences of the Angstrom exponents on size distribution are higher . The EAE AAE and SSAAE of coated BC by non absorptive materials with different particle size distributions change in ranges of 0.31.5 0.32.5 and 0.10.9 respectively . The core shell Mie model can hardly produce accurate results of the Angstrom exponents of coated BC particles especially the AAE and SSAAE . Our study reveals that BC coated by non absorbing materials with large size distribution of coated BC may show negative SSAAE values for some coating microphysics indicating the limitation of separating brown carbon from black carbon with a criterion of negative SSAAE .
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BC with non absorbing coating for large size distribution may show negative SSAAE. Importance of size distribution and shell core ratio on AE of coated BC is stressed. The angstrom exponents of aged BC are numerically studied with recent observations. Sensitivities of angstrom exponents of coated BC to its microphysics are studied. The core shell mie model hardly produces accurate angstrom exponents of coated BC.
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S0022407320306920
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We sketch the life and scientific legacy of Prof. Richard K. Chang 19402020 the Henry Ford II Professor of Applied Physics Professor of Physics and Electrical Engineering at Yale University . We briefly outline his research from linear and non linear optics light interactions with solids and liquids in various surface micro shapes and nano structures optical effects and processes in microresonators and later to laser spectroscopic characterization of sprays combustion and environmental pollutants . Prof. Chang has many colleagues collaborators students and friends among the JQSRT community .
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Scientific career and family life about Professor Richard K. Chang. Linear and non linear optics. Optical effects and processes in micro resonators. Laser spectroscopic characterization for airborne aerosol particles.
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S0022407320306993
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Extreme ultraviolet radiation of laser produced zirconium plasmas were measured in the 6.714.7nm region using a spatio temporally resolved laser produced plasma spectroscopy technique . At shorter wavelengths the spectrum was dominated by several lines attributed to the 4s transition arrays of Zr
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A spatio temporally resolved laser produced plasma spectroscopy technique have been used to study the laser produced zirconium Zr plasmas in the 6.714.7 nm region. The Hartree Fok HF method with relativistic corrections HFR using the Cowan s codes and Flexible Atomic Code FAC were used to calculate and interpret the observed spectral obtained. Accordingly a number of new spectral lines are identified. A numerical computation based on the assumption of a normalized Boltzmann distribution among the excited states associated with a steady state collisional radiative model CR has also been performed to obtain the plasma parameters by comparing the experimental and simulated spectra. Good agreement between the experimental and theoretical calculations were obtained. Temporal and spatial evolution behavior about plasma parameters have been analyzed and the variation of electron plasma frequency and skin depth with plasma temperature were introduced.
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S002240732030710X
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We report an experimental study of nonlinear radiation trapping in a high density rubidium vapor where the self broadening of the resonance transitions
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We report an experimental study of nonlinear radiation trapping in a high density rubidium vapor where the self broadening exceeded the Doppler broadening. We observe growing of the effective radiative lifetime with increasing optical power in dense gas. It was shown that incoherent optical saturation can be increased by the number of photon absorption reemission in the radiation transfer process. The radiation trapping effect helped to increase the incoherent saturation.
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S0022407320307342
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By means of laser spectroscopy and optogalvanic detection we searched for unknown spectral lines of atomic lanthanum in the red region of the visible spectrum . Most of the discovered lines could be interpreted as transitions between known energy levels due to wavelength and observed hyperfine structure pattern . For lines which we could not classify we searched for laser induced fluorescence in order to identify at least one level involved in the transition . In this way we discovered 25 energy levels of La I having even parity . For two levels we could improve the accuracy of energy and hyperfine structure constants . These 27 levels classify 213 spectral lines .
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Further investigation of the hyperfine structure constants of La I levels. Discovery of 25 new energy levels of lanthanum. Improvement of data of two further levels. Classification of 213 spectral lines. Application of laser spectroscopy with optogalvanic and laser induced fluorescence detection.
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S0022407320307470
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Haze incorporating abundant charged aerosol has become a main air problem in various metropolitan cities worldwide . Studying the propagation characteristics of electromagnetic wave in charged haze aerosol is conducive to calibrate instruments designed based on energy attenuation of EMW and is critical to providing guidance for deployment of network base stations . Here we simulated haze conditions by quantitatively controlling the concentration water content and charge quantity of aerosols in laboratory and first found that attenuation coefficient of EMW changes linearly with these factors . In addition we proposed a method to determine the complex dielectric constant of haze aerosols . Upon this a new model which combines the surface conductivity of a single particle at micro level with the charge density of the aerosol at macro level was developed to quantitatively evaluate the contributions of aerosol concentration water content and charges on the attenuation of EMW . The results show that when EMW propagates in charged haze aerosol its attenuation coefficient can be quantitatively characterized by mass concentration particle moisture and charge to mass ratio of aerosol . And the simulated results are in good agreement with the experiments .
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While electromagnetic EMW propagate in a haze containing charged aerosols the energy of EMW suffers attenuation. Here we simulate haze conditions by quantitatively controlling the concentration water content and charge quantity of aerosols. We are the first to determine that the attenuation coefficient of EMW changes linearly with all these factors. Then a new macroscopic model is presented to calculate the attenuation coefficient of EMW. Finally we not only demonstrate that our results are in good agreement with the experimental but also used this model to pro effective guidance in the deployment of networks base stations.
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S003442571830316X
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Reliable satellite monitoring of agriculture is often difficult because surface variations occur rapidly compared to the cloud free satellite observation frequency . Harmonic time series models i.e . superimposed sequences of sines and cosines have an established provenance for fitting satellite vegetation index time series to coarse resolution satellite data but their application to medium resolution Landsat data for crop monitoring has been limited . Non linear harmonic models have been shown to perform well over agricultural sites using single year Moderate Resolution Imaging Spectroradiometer time series but have not been explored with Landsat data . The 2017 availability of Landsat Analysis Ready Data over the United States provides the opportunity to investigate the utility of temporally rich Landsat data for 30m pixel level crop monitoring . In this paper the capability of 5 and 7 parameter linear harmonic models and a 5 parameter non linear harmonic model applied to a year of Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper Plus ARD is investigated . The analysis is undertaken over six sites each defined by a 50005000 30m pixel ARD tile that together include the major conterminous United States crops identified by inspection of the United States Department of Agriculture Cropland Data Layer . The model fits are evaluated as the root mean square difference between the fitted and the observed Landsat data . Considering locations with at least 21 annual Landsat observations the 7 parameter linear harmonic model and the 5 parameter non linear harmonic model are shown to be able to fit annual Landsat NDVI time series for most CONUS crops whereas the 5 parameter linear harmonic model can not . If there are between 15 and 20 annual Landsat observations the 5 parameter non linear harmonic model is recommended for fitting annual NDVI crop time series and if there are 21 observations then either the 5 parameter non linear or the 7 parameter linear model can be used . The 7 parameter model had marginally smaller mean NDVI RMSD values but larger standard deviations than the 5 parameter non linear model likely due to the relative robustness of the non linear model to over fitting and oscillations . None of the models could reliably fit crops with multiple stages such as alfalfa that are insufficiently sampled using combined Landsat 5 TM and Landsat 7 ETM time series . Given the utility of the growing season peak NDVI for crop yield applications the date and magnitude of the model fitted peak NDVI are compared to quantify model reporting differences . The differences between the 7 parameter linear and the 5 parameter non linear harmonic models are not large . For each ARD tile the mean absolute differences in the estimated peak NDVI days varied from 2days in the northern ARD tiles which had short growing seasons and similar crops to less than a week for the other tiles except for nearly 10days for the California tile that had longer growing seasons and more diverse crops including crops with multiple stages . The paper concludes with a discussion and recommendations for future research .
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Harmonic model fitting on crops using single year Landsat 5 and 7 time series. Landsat ARD data. First application of non linear harmonic model to Landsat time series. NDVI models fitted per pixel in six 50005000 30m agricultural ARD tiles. Considered all major U.S. crop types
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S0034425718303171
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Global repeat satellite imagery serves as an essential tool to understand ecological patterns and processes over diverse temporal and spatial scales . Recently the use of spaceborne imagery has become indispensable for monitoring giant kelp a globally distributed foundation species that displays variable seasonal and interannual dynamics . In order to develop and maintain a continuous and spatially expansive time series we describe a fully automated protocol to classify giant kelp canopy biomass across three Landsat sensors . This required correcting kelp canopy estimates to account for changes in the spectral response functions between the three sensors by simulating data using hyperspectral imagery . Combining multiple sensors also necessitated the use of an extended time series of diver estimated kelp biomass to validate each sensor . We also describe a novel gap filling technique using known spatial scales of kelp biomass synchrony to correct for missing data due to the Enhanced Thematic Mapper Plus scan line corrector failure . These developments have led to a publicly available 34 year seasonal time series of kelp canopy biomass across 1500km of California coastline .
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Developed a consistent kelp canopy biomass time series merging three Landsat sensors. Investigated and corrected for the role of tidal height in Landsat estimates. Developed a gap filling algorithm based on spatial synchrony patterns. Marine climate oscillations are associated with long term kelp biomass trends. Argues for longer continuous satellite records for the detection of climate change
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S0034425718304437
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The accurate retrieval of land surface vegetation properties under varying environmental conditions from time series of moderately high spatial resolution satellite observations is challenging . By coupling various Radiative Transfer models one can describe the soil vegetation and atmosphere contributions in a bottom up approach and thereby simulate top of atmosphere spectral radiance data comparable to satellite observed TOA radiances . This makes it possible to retrieve vegetation properties directly from TOA radiances rather than from atmospherically corrected top of canopy reflectance data . The advantages of this approach are that a separate atmospheric correction of the satellite images is not necessary and that the anisotropic surface reflection can also be taken into account effectively . In this study we coupled various RT models including the brightness shape moisture reflectance model of the soil the optical radiative transfer model of vegetation and the MODerate resolution atmospheric TRANsmission model of the atmosphere to simulate an annual time series of Landsat satellite TOA radiances observed during a drought episode in California Mediterranean grasslands in 2004 . The inversion of this coupled system through an optimization technique against Landsat TOA radiances resulted in direct retrieval of vegetation properties . We accommodated the surface anisotropic reflection in our coupled modeling and also defined a novel anisotropy index to quantitatively express the importance of this phenomenon in satellite image analysis for the first time . Our study showed that the coupled use of RT models was able to accurately reproduce the time series of observed TOA radiances collected under varying soil moisture contents during an extended drought episode . The proposed coupling approach is useful for successful retrieval of vegetation properties from time series of satellite TOA radiance data to produce maps of land surface properties and to monitor vegetation properties variations in an operational straightforward way . The approach can also be easily adapted for conducting multi sensor time series studies creating a much denser temporal sampling than would be possible for separate single sensors .
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Time series of Landsat TOA radiances simulated. A bottom up retrieval approach from TOA radiance is applied. Surface anisotropy quantified and accommodated by using TOA radiance approach. RT models coupled include BSM RTMo and MODTRAN5. The potential of monitoring water deficit from Landsat TOA radiance explored.
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S0034425718304590
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A novel method called Continuous Subpixel Monitoring was developed to map and monitor urban impervious surface change continuously at the subpixel level . Time series model of each pixel was first estimated based on clear Landsat observations between 2000 and 2014 and any land surface change was detected by the Continuous Change Detection and Classification algorithm . These coefficients and Root Mean Square Errors of the estimated time series models were then employed as the inputs of random forest regressor . A few experiments with different combinations of variables and bands were explored to better construct random forest regression models . We successfully applied this algorithm to map subpixel urban impervious surface area and characterize its dynamics in Broome County New York . Several conclusions can be drawn from the results and analyses . First the integration of subpixel mapping technique and time series analysis in CSM can yield a relatively satisfactory ISA result at one point in time . With higher precision and smaller bias its mapping accuracy is better than that of National Land Cover Database percent developed imperviousness product without using extensive auxiliary data such as nighttime light image and transportation network . Second the ISA change of any time interval can be easily derived and detected by CSM with relatively high accuracy which have the potential to generate sub annual ISA change products . Furthermore this approach can detect not only urban expansion intensification but also different patterns of urban transitions overtime such as urban demolition redevelopment to vegetation and surface modifications . Finally CSM works well in one of the cloudiest regions in the United States . This algorithm could provide a new direction to map and monitor percent urban impervious surface change in a reliable and efficient way which also has the potential to apply to other land cover types at the subpixel level .
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CSM allows continuous spatially and temporally monitoring at the subpixel level. Generated a time series cube with high accuracy to monitor subpixel impervious surface dynamics. CSM can automatically detect different patterns of urban transitions overtime. Training samples and trained random forest models were transferable with CSM. CSM works well in one of the cloudiest regions in the United States.
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S0034425718305200
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Tropical forest loss currently contributes 5 to 15 of anthropogenic carbon emissions to the atmosphere . The large uncertainty in emissions estimates is a consequence of many factors including differences in definitions of forests and degradation as well as estimation methodologies . However a primary factor driving uncertainty is an inability to properly account for forest degradation . While remote sensing offers the only practical way of monitoring forest disturbances over large areas and despite recent improvements in data quality and quantity and processing techniques remote sensing approaches are still limited in their ability to detect forest degradation . In this paper a system is presented that uses time series of Landsat data and spectral mixture analysis to detect both degradation and deforestation in forested landscapes . The Landsat data are transformed into spectral endmember fractions and are used to calculate the Normalized Degradation Fraction Index . The spectrally unmixed data are used for disturbance monitoring and land cover classification via time series analysis . To assess the performance of the system maps of deforestation and degradation were used to stratify the study area for collection of sample data to which unbiased estimators were applied to produce accuracy and area estimates of degradation and deforestation from 1990 to 2013 . The approach extends previous research in spectral mixture analysis for identifying forest degradation to the temporal domain . The method was applied using the Google Earth Engine and tested in the Brazilian State of Rondnia . Degradation and deforestation were mapped with 88.0 and 93.3 User s Accuracy and 68.1 and 85.3 Producer s Accuracy . Area estimates of degradation and deforestation were produced with margins of error of 13.9 and 5.3 respectively over the 24year time period . These results indicate that for Rondnia a decreasing trend in deforestation after 2004 corresponds to an increase in degradation during the same time period .
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A methodology is presented for detecting forest degradation and deforestation. The approach is based on spectral unmixing and time series analysis using Landsat. Unbiased area estimates are calculated from 1990 to 2013 for Rondnia Brazil. High precision is achieved on the area estimates of the disturbance classes. A decrease in deforestation in 2004 corresponded to an increase in degradation.
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S003442571830539X
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Tidal flats along with coastal vegetation area constitute the coastal wetlands between high and low water lines and play an important role in wildlife biodiversity and biogeochemical cycles . However accurate annual maps of coastal tidal flats over the last few decades are unavailable and their spatio temporal changes in China are unknown . In this study we analyzed all the available Landsat TM ETM OLI imagery using the Google Earth Engine cloud computing platform and a robust decision tree algorithm to generate annual frequency maps of open surface water body and vegetation to produce annual maps of coastal tidal flats in eastern China from 1986 to 2016 at 30 m spatial resolution . The resulting map of coastal tidal flats in 2016 was evaluated using very high resolution images available in Google Earth . The total area of coastal tidal flats in China in 2016 was about 731 170ha mostly distributed in the provinces around Yellow River Delta and Pearl River Delta . The interannual dynamics of coastal tidal flats area in China over the last three decades can be divided into three periods a stable period during 19861992 an increasing period during 19932001 and a decreasing period during 20022016 . The resulting annual coastal tidal flats maps could be used to support sustainable coastal zone management policies that preserve coastal ecosystem services and biodiversity in China .
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Mapping tidal flats in China for 19862016 using time series Landsat imagery. Spatial distribution of tidal flats in China in 2016. Temporal variations of tidal flats from 1986 to 2016 and its driving factors. Erosion and expansion of tidal flats in the Yellow River and Yangtze River Delta
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S0034425718305698
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Over the last 20years substantial amounts of grassland have been converted to other land uses in the Northern Great Plains . Most of land cover land use assessments in this region have been based on the U.S. Department of Agriculture Cropland Data Layer which may be inconsistent . Here we demonstrate an approach to map land cover utilizing multi temporal Earth Observation data from Landsat and MODIS . We first built an annual time series of accumulated growing degree days from MODIS 8 day composites of land surface temperatures . Using the Enhanced Vegetation Index derived from Landsat Collection 1 s surface reflectance we then fit at each pixel a downward convex quadratic model to each year s progression of AGDD
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Land surface phenology LSP modeled using Landsat EVI and MODIS LST. Land cover from random forest classification RFC using only phenometrics as input. Combinations of reference data augmented by CDL used for training validation. LSP RFC accurately identified major crops compared to the Cropland Data Layer CDL . Caveat alternative RFC training designs yielded widely varying area estimates.
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S0034425718305704
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Forest ecosystem services such as clean water wildlife habitat and timber supplies are increasingly threatened by drought and disturbances which can have great impacts on stand development and water balance . Improved understanding of the hydrologic response of forested systems to drought and disturbance at spatiotemporal resolutions commensurate with these impacts is important for effective forest management . Evapotranspiration is a key hydrologic variable in assessing forest functioning and health but it remains a challenge to accurately quantify ET at landscape scales with the spatial and temporal detail required for effective decision making . In this study we apply a multi sensor satellite data fusion approach to study the response of forest ET to drought and disturbance over a 7 year period . This approach combines Landsat and Moderate Resolution Imaging Spectroradiometer ET product time series retrieved using a surface energy balance model to generate a multi year ET datacube at 30 m resolution and daily timesteps . The study area 900km
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Impacts of drought and disturbance on forest are investigated using ET time series. The impact of drought on managed forest ET decreases with stand age. Stand disturbance and recovery signals are identified in ET based moisture stress. ET time series complement vegetation indices for monitoring land water use change.
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S0034425718305947
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The Bekaa Valley in Lebanon currently hosts the highest number of refugees per capita in the world . It is also the primary agricultural production area in the country . Groundwater levels in some regions of the valley have decreased by 15m in the last five years . Water use estimates at the regional and the field scale for this valley are crucial for enhancing resilience and for managing competing sectorial water demands . In this research we derive a novel time series of field scale actual evapotranspiration for the Bekaa Valley using two one source energy balance models for the period 19842017 utilizing local weather data and all available original Level 1 Landsat thermal imagery and Level 2 surface reflectance products . We compare a modified METRIC model with an automated hot and cold pixel identification procedure run in batch mode to pySEBAL a new version of SEBAL which also has its automated anchors pixel selection algorithm . Analysis of 1200 cloud masked and gap filled Landsat derived ET products show that the two models give comparable water use estimates at the seasonal and annual time steps . We estimate an average annual ET of 65253mm over the heavily cultivated valley in the last 34years . Most of the ET is consumed from blue water in the dry season of MayOctober . ET in the wet season of NovemberApril consumes 70 of the precipitation in the Bekaa valley . Annual analysis shows no discernable trend in ET across the valley but there is an increase in irrigated agriculture in the Orontes Basin in the last five years . METRIC yields 15 higher ET than pySEBAL for the non agricultural lands in summer . A water balance analysis shows that groundwater storage in the Litani basin is decreasing at a rate of 33050mmyr
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Full Landsat thermal collection utilized to generate field scale ET in Lebanon. Automated anchor pixel selection applied in METRIC and pySEBAL on 1200 scenes. Peak water use of 500mcm in the Bekaa is between April and August. No trends in time series ET determined for the Bekaa Valley for 19842017. Non renewable aquifer depletion ranges from 280 to 380mm per year.
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S0034425719300136
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The REDD mechanism of UNFCCC was established to reduce greenhouse gases emissions by means of financial incentives . Of importance to the success of REDD and similar initiatives is the provision of credible evidence of reductions in the extent of land change activities that release carbon to the atmosphere . The criteria for reporting land change areas and associated emissions within REDD stipulate the use of sampling based approaches which allow for unbiased estimation and uncertainty quantification . But for economic compensation for emission reductions to be feasible agreements between participating countries and donors often require reporting every year or every second year . With the rates of land change typically being very small relative to the total study area sampling based approaches for estimation of annual or bi annual areas have proven problematic especially when comparing area estimates over time . In this paper we present a methodology for monitoring and estimating areas of land change activity at high temporal resolution that is compliant with international guidelines . The methodology is based on a break detection algorithm applied to time series of Landsat data in the Colombian Amazon between 2001 and 2016 . A biennial stratified sampling approach was implemented to remove the bias introduced by the change detection and classification algorithm in mapped areas derived from pixel counting and provide confidence intervals for area estimates obtained from the reference data collected for the sample . Our results show that estimating the area of land change like deforestation at annual or bi annual resolution is inherently challenging and associated with high degrees of uncertainty . We found that better precision was achieved if independent sample datasets of reference observations were collected for each time interval for which area estimates are required . The alternative of selecting one sample of continuous reference observations analyzed for inference of area for each time interval did not yield area estimates significantly different from zero . Also when large stable land covers are present in the study area in combination with small rates of land change activity the impact of omission errors in the map used for stratifying the study area will be substantial and potentially detrimental to usefulness of land change studies . The introduction of a buffer stratum around areas of mapped land change reduced the uncertainty in area estimates by up to 98 . Results indicate that the Colombian Amazon has experienced a small but steady decrease in primary forest due to establishment of pastures with forest to pasture conversion reaching 10330kha in the period between 2013 and 2015 corresponding to 0.22 of the study area . Around 2917kha of pastureland that had been abandoned shortly after establishment reverted to secondary forest within the same period . Other gains of secondary forest from more permanent pastures averaged about 1211kha while losses of secondary forest averaged 2012kha .
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Presented methods allow for monitoring activities and post disturbance landscapes. Deforestation driven by conversion to pastures is increasing at very small rate. Less than a fifth of the area of deforestation was abandoned and left to regenerate. Using a buffer stratum around change areas increased precision in area estimates. Samples representing each period for which area estimates are desired were required.
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S0034425719301002
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We developed a new algorithm for COntinuous monitoring of Land Disturbance using Landsat time series . COLD can detect many kinds of land disturbance continuously as new images are collected and provide historical land disturbance maps retrospectively . To better detect land disturbance we tested different kinds of input data and explored many time series analysis techniques . We have several major observations as follows .
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We developed a new algorithm for continuous monitoring of land disturbance. All land disturbance types are detected in the disturbance map. Both omission and commission errors are 30 . No training data is needed for detecting land disturbance. Disturbance maps with high spatial and high temporal resolutions are derived.
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S0034425719301634
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An ensemble of time series algorithms improves land change monitoring . The methodology combines the Continuous Change Detection and Classification and Cumulative Sum of Residuals algorithms for break detection and the Chow Test for removing false positives . The algorithms included are based on fundamentally different approaches to change detection and therefore offer unique advantages . The ensemble or the combination of the three algorithms was applied to 3 Landsat scenes in the United States and the results were assessed based on their ability to correctly discern structural breaks from stable time periods . The CUSUM test was shown to detect significant breaks 84.18 of the time and the Chow Test correctly removed breaks in 87.4 of the breaks analyzed . The ensemble produced results with lower frequency of errors of omission and commission than a single algorithm approach . These results indicate that using a combination of break detection algorithms can be an improvement over typical approaches that utilize only one algorithm .
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Multiple approaches for detecting breaks in a time series are combined sequentially. The algorithms are applied in the context of land change monitoring. The break detection algorithms are CCDC CUSUM and the Chow Test. Two tests are used to detect breaks and one is used to identify false positives. Break detection is improved in over 84 of break locations tested.
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S0034425719302093
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For retrospective land cover change analysis extending back in time earlier than approximately the year 2000 multispectral remote sensing data such as the Landsat archive are often the only available and systematically archived data source . However the spatial resolution of such observations often impedes the change analysis of geographic phenomena that may occur at sub pixel level such as changes in built up land . In such cases the integration of these data products with increasingly available contemporary high resolution settlement data employed as spatial constraints can potentially mitigate this drawback . Little research has been done regarding the quantitative potential of such integrative approaches often due to the lack of multi temporal reference data about changes in built up area at sufficient spatio temporal granularity and extent . In this contribution we present and evaluate a time series based approach for built up area change analysis using Landsat time series data spatially constrained by contemporary building footprint data . We evaluate the potential of our approach using a highly accurate multi temporal reference database of built up areas created through integrating publicly available building footprint and cadastral data in selected regions of the United States of America .
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We propose a novel method for retrospective analysis of built up areas. We created a large multi temporal training validation database on built up land. Landsat time series data are integrated with cadastral and building footprint data. Our method makes use of machine learning techniques and curve fitting approaches. We compared supervised and unsupervised classification methods.
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S0034425719302809
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The U.S. Geological Survey Land Change Monitoring Assessment and Projection initiative is working toward a comprehensive capability to characterize land cover and land cover change using dense Landsat time series data . A suite of products including annual land cover maps and annual land cover change maps will be produced using the Landsat 4 8 data record . LCMAP products will initially be created for the conterminous United States and then extended to include Alaska and Hawaii . A critical component of LCMAP is the collection of reference data using the TimeSync tool a web based interface for manually interpreting and recording land cover from Landsat data supplemented with fine resolution imagery and other ancillary data . These reference data will be used for area estimation and validation of the LCMAP annual land cover products . Nearly 12 000 LCMAP reference sample pixels have been interpreted and a simple random subsample of these pixels has been interpreted independently by a second analyst . The annual land cover reference class labels for the 19842016 monitoring period obtained from these duplicate interpretations are used to address the following questions 1 How consistent are the reference class labels among interpreters overall and per class 2 Does consistency vary by geographic region 3 Does consistency vary as interpreters gain experience over time 4 Does interpreter consistency change with improving availability and quality of imagery from 1984 to 2016 Overall agreement between interpreters was 88 . Class specific agreement ranged from 46 for Disturbed to 94 for Water with more prevalent classes generally having greater agreement than rare classes . Agreement between interpreters remained approximately the same over the 12 month period during which these interpretations were completed . Increasing availability of Landsat and Google Earth fine resolution data over the 1984 to 2016 monitoring period coincided with increased interpreter consistency for the post 2000 data record . The reference data interpretation and quality assurance protocols implemented for LCMAP demonstrate the technical and practical feasibility of using the Landsat archive and intensive human interpretation to produce national annual reference land cover data over a 30 year period . Protocols to estimate and enhance interpreter consistency are critical elements to document and ensure the quality of these reference data .
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A subset of pixels with duplicate interpretations quantifies consistency. Interpreter agreement was 88 overall ranging from 46 Disturbed to 94 Water . Regional variation in class specific agreement was observed. Agreement stayed about the same as interpretations were finished over time. Agreement was greater for data after 2000 coinciding with increased data density.
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S0034425719302858
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The ongoing march toward freely available highly pre processed satellite imagery has given both researchers and the public unprecedented access to a vast and varied data stream teeming with potential . Among many sources the multi decade Landsat archive is certainly the best known but legacy and current data from other sensors is available as well through the USGS data portals these include CBERS ASTER and more . Though the particular band combinations or non global missions have made their integration into analyses more challenging these data in conjunction with the entire Landsat record are available to contribute to multi decade surveys of land cover change .
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We synthesized a 45 year LULC time series from 13 sensors for Roosevelt River Brazil. We quantified forest cover loss for agriculture and its recovery with high accuracy. Roosevelt River BZ until recently highly isolated was 10 deforested by 2016. Noisy image classifications may be highly useful especially in early satellite era.
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S0034425719303414
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In recent years large amount of high spatial resolution remote sensing images are available for land cover mapping . However due to the complex information brought by the increased spatial resolution and the data disturbances caused by different conditions of image acquisition it is often difficult to find an efficient method for achieving accurate land cover classification with high resolution and heterogeneous remote sensing images . In this paper we propose a scheme to apply deep model obtained from labeled land cover dataset to classify unlabeled HRRS images . The main idea is to rely on deep neural networks for presenting the contextual information contained in different types of land covers and propose a pseudo labeling and sample selection scheme for improving the transferability of deep models . More precisely a deep Convolutional Neural Networks is first pre trained with a well annotated land cover dataset referred to as the
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A method to learn transferable deep model for 5 class land cover LC classification. A labeled dataset consisting of 150 Gaofen 2 images for LC classification. It improves LC classification performance about 20 using multi source RS images. The method shows good transferability on different sensors and geolocations.
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S0034425719304341
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Increasing evidence suggests that ecosystem functions are strongly linked to morphological plant traits like specific leaf area and its variability which serve as a proxy of functional diversity . Functional diversity is rarely studied at regional scales and its scale dependence is poorly understood . Capturing trait variations at distinct spatial scales and in differently managed grasslands remains challenging mainly because a limited number of trait measurements are available and field campaigns are time consuming . Here we derived and FD indices based on SLA measured in the field and estimated from optical satellite data by using molecular absorption profiles of leaves in canopies . We inverted the 1 D columnar radiative transfer model PROSAIL using Sentinel 2 reflectance data at canopy level . From the inversion we were able to distinguish different alpine management types based on retrieved SLA . Model uncertainties were mainly related to the different local plant communities here represented by functional diversity indices and community weighted means of traits . Thus successful PROSAIL application was affected by management type . Management categories displaying lower FD like
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CWM of SLA estimable from Sentinel 2 datasets with PROSAIL. Alpha functional diversity influences remotely sensed plant trait retrieval. It is crucial to quantify an area wide beta functional diversity. Management types impact spatial components of functional diversity differently.
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S0034425719304377
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Southern Tunisia is one of the most significant areas of historical and archaeological interest as since the Roman period it has played a key role as a land bridge controlling the passage from the Saharan plain to plateaus and to the north of the mountain range between Chebika and Metlaoui . Because of the difficult geography the investigation of ancient sites in this region is not easy and therefore satellite based investigation can play an important role in the detection and documentation of archaeological sites . In this study we combined high resolution remote sensing imagery with in situ investigations to assess the suspected archaeological sites detected using satellite data and historical documentation . The suspected sites were confirmed according to the geometric features of the sites as they appeared in the remotely sensed imagery these sites had not been detected during earlier field investigations . In particular we aimed to use 1 m spatial resolution WorldView 2 imagery of the Wadi El MelahValley in Gafsa . The satellite data were processed using statistical analysis and unsupervised classification.WV2 satellite imagery of WMV Southwestern Tunisia was processed within ArcGIS 10.2 to identify spatial features linked to the sites . The study outlines three different feature extraction methods . The satellite based analysis and archaeological records were evaluated by RS and GIS prospecting in the area of the field survey to confirm the new discoveries . The results of remotely sensed data combined with field survey enabled us to reconstruct the military defense system consisting of is a linear defensive structure and forts related to the Imperial Roman period . Taken together the results of our investigations provide new insights into some important sections of the Roman limes in the southern part of the empire . Other concealed remains are still to be found and explored .
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Exploring the Roman military system using WorldView 2 imagery and in situ data. Automatic identification of unknown archaeological features in south Tunisia. Towards an operative use of remote sensing in landscape archaeology. Knowledge improvement on the south border of ancient Roman.
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S0034425719304389
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Drought indices based on thermal remote sensing have been developed and have merit for effective early warning of agricultural droughts but approaches so far are relatively complex or sensitive to land surface temperature estimation uncertainties . Here we propose the temperature rise index a drought index that is comparatively robust and easy to calculate as the anomaly of the intrinsic morning rise of LST . The underlying principle is that the rate of LST rise between 1.5 and 3.5h after the sunrise is approximately linear and occurs more rapidly under dry conditions than under wet conditions over vegetated surfaces as a consequence of stomatal control . TRI during the growing seasons of 20102014 was calculated over the Australian wheatbelt from LST retrievals from the geostationary Multifunction Transport Satellite 2 instrument . The calculated TRI was compared with indices based on precipitation integrated over 1 3 and 6 month time scales on Soil Moisture and Ocean Salinity soil moisture derived from passive microwave remote sensing and on vegetation condition derived from optical remote sensing . The various indices were also compared to annual wheat yield over large areas . The correlation coefficient between TRI and precipitation anomaly that serves as an operational drought index in Australia was above 0.6 in general with 3 month integrative time scale for precipitation . TRI produced spatiotemporal dryness patterns that were very similar to those in soil moisture but with more detail due to its finer resolution . A time lag of 1 month was found between TRI and observed vegetation condition supporting the use of TRI in early warning . Among the compared drought indices TRI explained the largest fraction of wheat yield variations . TRI correlations with wheat yields peaked higher and earlier by almost one month in comparison to other indices . We conclude that the thermal drought index proposed here shows considerable potential for use in drought early warning as an effective complement .
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Land surface temperature morning rise at 1.53.5h after sunrise is quasi linear. Vegetation canopy under water stress has a faster temperature morning rise. Temperature rise index provides earlier drought monitoring than greenness indices. Temperature rise index peaked higher and earlier by 1 month in correlation to yields.
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S0034425719304390
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Remote sensing of solar induced chlorophyll fluorescence provides great potential for estimating gross primary production of terrestrial ecosystems . A strong relationship between SIF and GPP has been observed at the seasonal scale from both ground based and satellite observations . However variations of SIF due to changes in plant growth stages appear to influence the SIF GPP relationship . It remains unclear how this relationship is affected by plant growth related changes especially for C4 plants such as maize . In this study continuous
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Continuous ground measurements of SIF were obtained in a maize field. Asymmetrical response of SIF and GPP to PAR was observed under sunny days. SIF GPP relationship varies with plant growth stage. Canopy structure influences the SIF GPP and SIF. LUE relationships.
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S0034425719304407
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Satellite Synthetic Aperture Radar is an operational tool for monitoring and assessment of oil spills . Satellite SAR has primarily been used to detect the presence absence of oil yet its ability to discriminate oil emulsions within a detected oil slick has not been fully exploited . Additionally one of the challenges in the past has been the ability to deliver strategic information derived from satellite remote sensing in a timely fashion to responders in the field . This study presents methods for the rapid classification of oil types and estimated thicknesses from which information about thick oil and oil emulsions can be delivered in an operational timeframe to responders in the field . Experiments carried out at the OHMSETT test facility in New Jersey demonstrate that under specific viewing conditions a single polarization satellite SAR image can record a signal variance between thick stable emulsions and non emulsified oil . During a series of field campaigns in the Gulf of Mexico with in situ measurements of oil thickness multiple satellite data were obtained including fully polarimetric C band SAR imagery from RADARSAT 2 and multispectral imagery from ASTER and WorldView 2 . One campaign included the airborne polarimetric UAVSAR L band sensor . An oil emulsion thickness classification product was generated based on RADARSAT 2 polarimetric imagery using entropy and the damping ratio derivations . Herein we present the classification methods to generate oil thickness products from SAR validated by sea truth observations the multispectral imagery and the UAVSAR data . We tested the ability to deliver these products with minimum latency to responding vessels via NOAA . During field operations in the Gulf of Mexico a satellite SAR based product of oil delineation by relative thickness was delivered to a responding vessel 42min after the RADARSAT 2 data acquisition . This proof of concept test using satellite SAR and multispectral imagery to detect emulsions and deliver a derived information product to a vessel in near real time points directly to methods for satellite based assets to be used in the near future for oil spill tactical response operations .
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Synthetic Aperture Radar satellite is capable of detecting oil spill emulsions. Oil Thickness Classifications are delivered to a vessel in near real time. Fully polarimetric Quadpol generated an oil emulsion thickness classification. Physical oil thickness measurements are used to validate classifications
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S0034425719304432
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This paper presents the forward modelling aspects of the SMOS activities at ECMWF . Several parameterizations of the Community Microwave Emission Modelling Platform are used to simulate L band Brightness Temperatures and compared to the SMOS TBs for 20102011 . We show that simulated TBs are primarily sensitive by order of importance to the soil roughness model the vegetation opacity and the soil dielectric model . In particular best CMEM results are obtained with the simple Wigneron soil roughness model and the Wigneron model for the vegetation opacity . For the soil dielectric model performances of the Wang and Schmugge and the Mironov models are shown to be similar and better than the Dobson model . The Wang and Schmugge model is then used in the next steps of this paper combined with the Wigneron roughness and vegetation models . The paper describes a multi angular multi polarised bias correction method based on a linear rescaling computed at the monthly scale using SMOS observations and ECMWF CMEM re analysed TBs for a four year period . Results show that for 20102013 the seasonal multi angular multi polarisation bias correction approach reduces global RMSE to 7.91K compared to 16.7K before bias correction whereas the mean absolute bias is reduced to 1.39K compared to 11.04K before bias correction . The consistency between the seasonality of simulated and the observed TBs is also improved by using a monthly bias correction leading to correlation values improvement to 0.62 after bias correction compared to 0.56 before . The 20102013 bias correction applied to the 20142016 period at 40 incidence reduces the global RMSE from 15.56K to 8.19K and the mean absolute bias from 10.16K to 2.51K with no impact on the correlation values that remain at 0.61 in both cases . Long term monitoring of SMOS TB is presented covering a 7 year period at both polarisations at 40 incidence angle . Results show that the consistency between SMOS and ECMWF reanalysis based TBs progressively improved between 2010 and 2016 pointing out improvements of level 1 SMOS TB products quality through the SMOS lifetime .
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A forward operator is used to simulate L band brightness temperatures. Bias correction corrects differences between observations and model. Multi angular and seasonal matching of cumulative distribution function is developed. Reanalysis of simulated forward brightness temperature used for SMOS monitoring. Long term monitoring of SMOS brightness temperatures shows improved SMOS data quality.
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S0034425719304626
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Remote sensing of night light emissions in the visible band offers a unique opportunity to directly observe human activity from space . This has allowed a host of applications including mapping urban areas estimating population and GDP monitoring disasters and conflicts . More recently remotely sensed night lights data have found use in understanding the environmental impacts of light emissions including their impacts on human health . In this review we outline the historical development of night time optical sensors up to the current state of the art sensors highlight various applications of night light data discuss the special challenges associated with remote sensing of night lights with a focus on the limitations of current sensors and provide an outlook for the future of remote sensing of night lights . While the paper mainly focuses on space borne remote sensing ground based sensing of night time brightness for studies on astronomical and ecological light pollution as well as for calibration and validation of space borne data are also discussed . Although the development of night light sensors lags behind day time sensors we demonstrate that the field is in a stage of rapid development . The worldwide transition to LED lights poses a particular challenge for remote sensing of night lights and strongly highlights the need for a new generation of space borne night lights instruments . This work shows that future sensors are needed to monitor temporal changes during the night and to better understand the angular patterns of light emission . Perhaps most importantly we make the case that higher spatial resolution and multispectral sensors covering the range from blue to NIR are needed to more effectively identify lighting technologies map urban functions and monitor energy use .
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Remote sensing of night lights allows observation of human activity from space. We provide a historical overview of the development of such night time sensors. We highlight various applications of remote sensing of night lights. We discuss the special challenges associated with remote sensing of night lights. We provide an outlook for the future of remote sensing of night lights.
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S003442571930464X
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The Atacama Desert is considered as one of the driest places on Earth . At the coastline however small scale fog oases harbor a specialized vegetation and fauna living from moisture by fog which is used by humans to feed water demands of industrial projects . To date knowledge about fog and low stratus clouds as well as their physical properties is limited in that only local observations or spatial products from satellites with coarse resolutions are available generally failing to capture local patterns resulting from the complex topography . Consequently we provide the first climatology of FLS with 30m spatial resolution based on over 400 Landsat scenes acquired since 1986 . The new product provides valuable estimates of FLS optical and micro physical properties . FLS over the Pacific Ocean featured cloud optical depth values around 13.5 declining over land to 4.2 . Effective radii were around 5.3m . Liquid water path was between 71.0
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New 30m spatial resolution product for fog low stratus optics and micro physics. Excellent agreement to low resolution existing products over homogeneous surfaces. Terrain affects clouds causing differences between new and existing products. According to local measurements the new product outperforms existing ones. Clouds over rugged terrain are underestimated by MODIS products.
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S0034425719304651
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Cloud detection algorithms are crucial in many remote sensing applications to allow an optimized processing of the acquired data without the interference of the cloud fields above the surfaces of interest . While this is a well established area of research replete with a number of cloud detection methodologies many issues persist for detecting clouds over areas of high albedo surfaces detecting cloud shadows and transferring a given algorithm between observational platforms . Particularly for the latter algorithms are often platform specific with corresponding rule based tests and thresholds inherent to instruments and applied corrections . Here we present a convolutional neural network algorithm for the detection of cloud and cloud shadow fields in multi channel satellite imagery from World View 2 and Sentinel 2 using their Red Green Blue and Near Infrared channels . This algorithm is developed within the NASA NeMO Net project a multi modal CNN for global coral reef classification which utilizes imagery from multiple remote sensing aircraft and satellites with heterogeneous spatial resolution and spectral coverage . Our cloud detection algorithm is novel in that it attempts to learn deep invariant features for cloud detection utilizing both the spectral and the spatial information inherent in satellite imagery . The first part of our work presents the CNN cloud and cloud shadow algorithm development and its application to WV 2 and to S 2 imagery . The second part presents a new domain adaptation CNN based approach that allows for better adaptation between the two satellite platforms during the prediction step without the need to train for each platform separately . Our augmented CNN algorithm results in better cloud prediction rates as compared to the original S 2 cloud mask but still clear pixels prediction rate is lower than S 2 . Nevertheless the application of the domain adaptation approach shows promise in better transferring the knowledge gained from one trained domain to another increasing the prediction accuracy of both clear and cloudy pixels when compared to a network trained only by WV 2 . As such domain adaptation may offer a novel means of additional augmentation for our CNN based cloud detection algorithm increasing robustness towards predictions from multiple remote sensing platforms . The approach presented here may be further developed and optimized for global and multi modal satellite cloud detection capability by utilizing a more global dataset .
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Convolutional Neural Networks CNNs are used for cloud and cloud shadow detection. CNN based cloud detector exploits both spatial and spectral data for high accuracy. Our CNN based method does not rely on SWIR or thermal IR bands. Our CNN based method trained on WV 2 succeeded in predicting Sentinel clouds. Our DANN based method improved Sentinel cloud predictions based on WV 2 training.
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S0034425719304663
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Traditionally the history of remote sensing began during the First World War when aerial photography became a valuable reconnaissance tool . However moving back more than a thousand years the real pioneers of remote observation were probably the Nasca a pre Hispanic civilization living in southern Peru between 100BC and 700 AD . They used earth observation as a mean of cultural expression drawing the geoglyphs only visible from above . These drawings were made on flat desert surface of the Pampa by removing or clearing sand or stones to create paths for ritual functions to please the gods and create harmonious relationships between man and environment . In this paper the Nasca geoglyphs in Pampa de Atarco are object of remote sensing based investigations with the twofold aim to identify and characterize them as well as to analyse and monitor their fragile state of conservation threatened mainly by vandalism and off road vehicles . The approach herein proposed includes the integration and reuse of diverse remote sensing dataset from multispectral satellite to Unmanned Aerial Vehicle based LSAR data and close range photogrammetry . In particular a multidate very high resolution optical satellite dataset has been processed in the spatial and temporal domain using textural indicators including Skewness Principal Component Analysis and automatic classification tools which allowed us to enhance the visibility of disturbance features and to automatically extract them . The best results in terms of enhancement and automatic extraction capability of disturbance features have been obtained by Skewness . Moreover the reuse of UAV L SAR based correlation map available free of charge from NASA provided useful information on the state of disturbance from 2013 to 2015 widening the observation time window of the VHR satellite data set from 2002 to 2013 . Finally the integrated use of satellite VHR data with UAV based photographs and DTMs processed using structure from motion allowed us to characterize identify and reconstruct the relative chronological sequence of geoglyphs thus providing new insights and opening new perspectives for archaeological studies .
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Exploring the past using the integration of satellite aerial and UAV data. Towards an operation satellite based monitoring of Nasca lines. Automatic classification of changes due to human induced disturbance. Relative chronology of execution phases of geoglyphs.
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S0034425719304778
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Functional zone reflects city s spatial structures and as a carrier of social and economic activities it is of critical significance to urban management resource allocation and planning . However most researches on functional zone division are based on a large spatial scale such as blocks or other scales larger than it . Aiming at a subtle fine functional result the concept of Super Object was especially explained also a Super Object Convolutional Neural Network based urban functional zone fine division method with very high resolution remote sensing image was proposed . The original image was firstly segmented into different SOs which correspond to the basic functional zone units in geography . A random point generation algorithm was used to generate the voting points for functional zone category identification and then a trained CNN model was employed to assign functional attributes to those voting points . Then a statistical method was involved to count the frequency of the classified voting points of different functional attributes in each basic functional zone units . By voting process the functional attribute with the highest frequency was assigned to the basic functional zone unit which corrected the misclassification results of CNN to some extent . This paper also explored the scale effect of the SO on the final functional zone classification result from two aspects spatial scale of SO and the sampling window size of CNN model . Because of the natural differences between functional zone division and land cover classification region based overall accuracy assessment method was used to evaluate functional zone division result . Compared with other methods SOCNN method can generate higher accuracy and subtle result based on which larger spatial scale results can be available by scaling up so SOCNN method plays a great significant role on small scale functional space structure research .
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Stressing the concept of Super Object SO . SOCNN combining voting strategy was proposed. Finer functional zone division result can be obtained. Exploring optimal scale and image resolution of functional zone division. Discussing accuracy evaluation methods for functional zone.
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S0034425719304857
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An accurate estimation of biomass burning emissions is partially limited by the lack of knowledge of fire burning phase . In recent years several fire detection products have been developed to provide information of fire radiative power location size and temperature of fire pixels but no information regarding fire burning phase is retrieved . The Day Night band aboard Visible Infrared Imaging Radiometer Suite is sensitive to visible light from flaming fires in nighttime scenes . In contrast VIIRS 4m moderate resolution band 13 though capable of detecting fires at all phases has no direct sensitivity for discerning fire phase . However the hybrid usage of VIIRS DNB and M bands data is hampered by their different scanning technology and spatial resolution . In this study we present a novel method to rapidly and accurately resample DNB pixel radiances to the footprint of M band pixels accounting for onboard detector aggregation schemes and bowtie effect removals . The visible energy fraction is subsequently introduced as an indicator of fire burning phase . VEF is calculated as the ratio of visible light power to FRP for each fire pixel retrieved from the VIIRS 750m active fire product . A global distribution of VEF values is quantitatively obtained showing smaller VEF values in regions with mostly smoldering wildfires such as peatland fires in Indonesia larger VEF values in regions with flaming wildfires over grasslands and savannas in the sub Sahelian region and the largest VEF values associated with gas flaring in the Middle East . Mean VEF for different land cover types or regions is highly correlated with modified combustion efficiency . These results together with a case study of the 2018 California Camp Fire show that the VEF has the potential to be an indicator of fire combustion phase for each fire pixel appropriate for estimating emission factors at the satellite pixel level .
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Novel approach to resample VIIRS Day Night Band radiances to its M band footprint. Visible energy fraction VEF concept is mathematically defined for nighttime fires. VEF is more effective than fire radiative power to describe fire phase. VEF is a strong indicator of the modified combustion efficiency MCE of fires. VEF is computed globally and captures MCE global variation for different biomes.
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S0034425719304912
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In recent years the concept of Local Climate Zones has become a new standard in the research of urban landscapes . LCZs outline a classification scheme which is designed to categorize urban and rural surfaces according to their climate relevant properties irrespective of local building materials or cultural background . We present a novel workflow for a high resolution derivation of LCZs using multi temporal Sentinel 2 composites and supervised Convolutional Neural Networks . We assume that CNNs due to their potential invariance to size and illumination of objects are best suited to predict the highly context based LCZs on a large scale . As a first step the proposed workflow includes a fully automated generation of cloud free S2 composites . These composites serve as training data basis for the LCZ classifications carried out over eight German cities . Results show that by using a CNN overall accuracies can be increased by an average of 16.5 and 4.8 percentage points when compared to a pixel based and a texture based Random Forest approach respectively . If sufficient training data is available CNN models proved to be robust in classifying unknown cities and achieved overall accuracies of up to
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A semi automatic workflow for LCZ classification based on Sentinel 2 and CNNs. High resolution mapping and detailed discussion of 14 LCZs in eight German study areas. Proposed CNN outperforms random forest approaches in terms of mapping accuracy.
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S003442571930495X
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Strong earthquakes especially in continental mountainous areas can trigger extensive mass wasting producing large amounts of debris that accumulates along the hillslopes or in drainage channels . The coseismic deposits and disturbed slopes are prone to be reactivated or remobilized by heavy rainfalls in the subsequent years after the earthquake . Predicting how long post seismic landslide activity will return to the pre earthquake level is a key to risk assessment and management . However this is still poorly understood and lacks quantitative prediction approach . The 2008 Wenchuan earthquake triggered an unprecedented number of landslides creating an extraordinary natural laboratory to investigate the evolution of post seismic landslides and their impacts on environment . Using the vegetation recovery rate as an indicator we present the observational evidence of the post seismic landslide evolution based on MODIS NDVI time series between 2000 and 2018 . Using a simple vegetation recovery rate function we quantify the rate of vegetation regrowth in the Wenchuan earthquake affected area and discuss the decaying trend of post seismic landslide activities . Our findings show that 83 of the co seismic landslides become inactive within a decade . The NDVI trend suggests that landslide activity may return to the pre earthquake level within 18 years . The sensitivity of vegetation regrowth to post seismic landsliding thus offers a great potential to improve our understanding of the spatio temporal evolution of the post seismic landslide activities .
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First decadal time series analysis is carried after 2008 Wenchuan M. 7.9 earthquake. NDVI. is proposed to minimize uncertainty in the vegetation damage area estimation. Vegetation recovery rate function is used to locate active and inactive landslides. Recovery of vegetation to the pre earthquake level is expected within 18 years.
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S0034425719304961
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Land surface phenology has been widely used as the footprint of urbanization and global climate change . Shifts of LSP have cascading effects on food production carbon sequestration water consumption biodiversity and public health . Previous studies mainly focused on investigating the effects of urbanization on the spatial patterns of LSP by comparing phenological metrics e.g . start of season and end of season between urban center and the surrounding rural regions . However it remains unclear how urbanization induced land cover conversions and climate change jointly influence the temporal variations of SOS and EOS within the urban ecosystem . To fill this knowledge gap we utilized daily two band enhanced vegetation index daily meteorological record and annual land cover dataset to investigate the respective impacts of urbanization and climate change on temporal shifts of LSP between the post and the pre urbanization periods over 196 large cities in the northern mid latitudes . We found 51 of the cities experienced an advanced SOS with an average of 6.395.82 days after urbanization has occurred while the remaining 49 of the cities had a delayed SOS with an average of 7.565.63 days . We also found a later EOS at 53 of the cities and an earlier EOS at 47 of the cities with an average of 8.437.59 and 5.574.99 days between the post and pre urbanization periods respectively . Multiple linear regression analysis indicates that climate variables play dominant roles in regulating the temporal shifts of LSP . Furthermore the earlier SOS and later EOS were significantly correlated with the amplitude of urbanization in cities after controlling for effects of climate factors . These patterns were generally consistent across eight climate zones . Our findings provide critical information in modeling natural and anthropogenic effects on urban ecosystem with important benefits for urban sustainability and biodiversity conservation .
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Post and pre urbanization periods were identified for 196 large cities. Half of the cities experienced earlier SOS and delayed EOS after urbanization. Climate change played a dominant role in regulating temporal shifts of phenology. Urbanization can either amplified or off set climate effects on phenology. Influences of urbanization and climate change vary by climate background.
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S0034425719304985
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Leaf chlorophyll is central to the exchange of carbon water and energy between the biosphere and the atmosphere and to the functioning of terrestrial ecosystems . This paper presents the first spatially continuous view of terrestrial leaf chlorophyll content Chl
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Global terrestrial leaf chlorophyll content maps are produced from satellite data. A two stage radiative transfer model inversion method is used. The algorithm was extensively validated with 248 measurements covering six biomes. Validation results are strong R. 0.47 RMSE 10.79gcm. 000.1 . Seasonal chlorophyll phenologies are visible from weekly data.
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S0034425719305000
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Satellite observations are used to detect surface waters but uncertainties such as instrument noise or retrieval errors can introduce noise or missing data in the resulting water maps especially for datasets at the global scale . In this study spatial filters based on several
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Sources of. surface water are introduced to improve satellite water maps. Topography floodability index spatial and. constraints are considered. A determinist data filling technique is proposed for missing data. A determinist noise filtering is introduced too. These 2 methods are tested over synthetic Sentinel 1 SAR and Sentinel 2 Visible data.
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S0034425719305012
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The worldwide demand for timely and accurate information about ecosystem dynamics at Landsat spatial scale is growing and as of today still exceeds the availability of information . The diversity of required disturbance metrics and trade offs between sensitivity reliability timelines of information generation and flexibility toward potential customizations suggests that a single system is not likely to fill such demand in the near future . To address this challenge the scientific community has been developing and improving various Landsat based algorithms for land change monitoring . We describe the Ecosystem Disturbance and Recovery Tracker version 2.9 a highly automated prototype system in continuous development which has been operated since 2012 by the USDA Forest Service Pacific Southwest Region to generate most current disturbance maps at Landsat scale and provide customized information services and inputs to science and land management applications in the Region .
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eDaRT maps disturbance events status in California to inform forest managers. Works on dense image time series from Landsat satellites. Processing data along multispectral contextual and temporal dimensions. eDaRT 2.9 system and algorithms are presented. High performance observed in tests with 35 000 reference samples.
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S0034425719305024
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The drainage divides of ice sheets separate the overall glaciated area into multiple sectors . These drainage basins are essential for partitioning mass changes of the ice sheet as they specify the area over which basin specific measurements are integrated . The delineation of drainage basins on ice sheets is challenging due to their gentle slopes accompanied by local terrain disturbances and complex patterns of ice movement . Until now in Greenland the basins have been mostly delineated along the major ice divides which results in large drainage sectors containing multiple outlet glaciers . However when focusing on measuring glaciological parameters of individual outlet glaciers more detailed drainage basin delineations are needed . Here we present for the first time a detailed and fully traceable approach that combines ice sheet wide velocity measurements by Sentinel 1 and the high resolution TanDEM X global DEM to derive individual glacier drainage basins . We delineated catchments for the Northeast Greenland Ice Sheet with a modified watershed algorithm and present results for 31 drainage basins . Even though validation of drainage basins remains a difficult task we estimated basin probabilities from Monte Carlo experiments and applied the method to a variety of different ice velocity and DEM datasets finding discrepancies of up to 16 in the extent of catchment areas . The proposed approach has the potential to produce drainage areas for the entirety of the Greenland and Antarctic ice sheets .
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A method to delineate drainage basins for individual outlet glaciers is proposed. The catchment delineation relies on a modi ed watershed algorithm. TanDEM X elevations and Sentinel 1 ice velocities are used for the delineation. The Northeast Greenland Ice Sheet is partitioned into 31 catchments.
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S0034425719305048
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A statistical regression based microwave sea surface temperature retrieval algorithm has been developed within the European Space Agency Climate Change Initiative SST project . The retrieval algorithm was used to generate a climate data record of passive microwave SST from the Advanced Microwave Scanning Radiometer Earth Observing System and its follow on instrument AMSR2 for the period June 2002October 2017 . Multisensor Matchup Datasets which includes satellite orbital data collocated with in situ and auxiliary data was used to derive consistent algorithms for AMSR E and AMSR2 . The retrieval algorithms consist of wind speed retrievals and SST retrievals with corresponding uncertainty retrievals . The WS retrieval consists of a two step regression model where the second step is a localized algorithm trained to perform well over restricted WS intervals . A two step multiple linear regression retrieval with localized algorithms is used to retrieve SST . The first stage algorithm is trained to perform well over restricted latitude intervals for ascending and descending orbit respectively whereas the second stage retrieval uses localized SST and WS algorithms . Furthermore a new and effective method for detecting and screening for Radio Frequency Interference was developed .
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Generation of a passive microwave sea surface temperature climate data record. Validation of AMSR E SSTs found a bias of 0.02K and standard deviation of 0.46K. A bias of 0.002K and standard deviation of 0.45K was for AMSR2 SST retrievals. AMSR E retrieved SST uncertainties are estimated to 0.45K. Retrieved SST uncertainties for AMSR2 are estimated to 0.44K.
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S0034425719305073
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Lodging the bending of crop stems reduces the quantity and quality of cereal crop yields . Early quantification of crop lodging is important to prevent further losses and to facilitate harvesting operations . Crop angle of inclination is a quantitative measure of the lodging stage and a component of lodging severity score . CAI is an important structural parameter for lodged crops and very few studies have investigated its estimation using satellite based remote sensing . In this study the performance of Sentinel 1 and multi incidence angle RADARSAT 2 data were investigated for estimating CAI . Temporal crop biophysical structural parameters and meteorological data were collected throughout May 1 June 30 2018 in a very large commercial farm located in Jolanda di Savoia Ferrara Italy . Field data were grouped into different crop lodging stages moderate lodging severe lodging and very severe lodging based on CAI . Quantitative relationships were established between field measured CAI values and the RS derived metrics for Sentinel 1 and RADARSAT 2 timeseries using support vector regression models . The RADARSAT 2 FQ8 model performed most robustly with a R
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An approach for quantitative assessment of lodging stages in wheat is presented. The relationship between the crop angle of inclination and SAR metrics were examined. The comparative performance of Sentinel 1 and RADARSAT 2 data was analyzed. RADARSAT 2 low incidence angle model performed most robustly with R. of 0.87.
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S0034425719305085
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Amazon forest leaf phenology patterns have often been inferred from the Moderate Resolution Imaging Spectroradiometer Enhanced Vegetation Index . But reliable MODIS detection of seasonal and interannual leaf phenology patterns has also been questioned and is generally not validated with field observation . Here we compare inter annual patterns of local scale upper canopy leaf phenology and demography derived from tower mounted phenocams at two upland forest sites in the Central Amazon to corresponding satellite vegetation indices retrieved from MODIS MAIAC . We focus on forest response to an unprecedented drought caused by the El Nio of 2015 16 . At both sites multi year phenocam data showed post drought shifts in leaf demography . These were consistent with MODIS MAIAC anomalies in two vegetation indices . Specifically a precocious leaf flush at both sites during the first two post drought months Feb Mar 2016 caused an anomalous decrease in flushing trees in JunJul of 2016 and an increase of trees with early mature stage leaves in Apr May Jun of 2016 . At both sites these two phenological anomalies showed up in MODIS MAIAC as respectively a strong negative anomaly in Gcc which prior work has shown to be sensitive to the abundance of leaves 0 1mo old and a strong positive anomaly in EVI which is sensitive to abundance of leaves 2 4mo age . A shift to sub optimal seasonal leaf age mix is expected to change the ecosystem scale intrinsic photosynthetic capacity for 18 month after the drought .
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Modis interannual and seasonal variation in tropical forest greenness is debated. Drought and high temperatures occurred during 2015 16El Nio in the Central Amazon. Tower mounted phenocams and MODIS MAIAC vegetation indices assessed leaf phenology. Both detect a cascade of anomalies set off by post drought precocious leaf flush. Shifted leaf demography may attenuate photosynthesis seasonality over following year.
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S0034425719305115
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Information on Earth s land surface and change over time has never been easier to obtain but making informed decisions to manage land well necessitates that this information is accurate and precise . In recent years due largely to the inevitability of classification errors in remote sensing based maps and the marked effects of these errors on subsequent area estimates sample based area estimates of land cover and land change have increased in importance and use . Area estimation of land cover and change by sampling is often made more efficient by
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Literature recommendations related to sampling based estimation are augmented. Omissions of land change in maps can introduce large uncertainty in area estimates. If stratifying by map class omissions of change tend to carry large area weight. Substrata in forest strata unlikely to contain error mitigate effects of omissions. Constructing efficient stratifications mitigate effects of omissions.
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S0034425719305127
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This paper presents the generation of a global burned area mapping algorithm using MODIS hotspots and near infrared reflectance within ESA s Fire cci project . The algorithm is based on a hybrid approach that combines MODIS highest resolution near infrared band and active fire information from thermal channels . The burned area is detected in two phases . In the first step pixels with a high probability of being burned are selected in order to reduce commission errors . To do that spatio temporal active fire clusters are created to determine adaptive thresholds . Finally a contextual growing approach is applied from those pixels to the neighbouring area to fully detect the burned patch and reduce omission errors . The algorithm was used to obtain a time series of global burned area dataset covering the 20012018 period . Validation based on 1200 sampled sites covering the period from 2003 to 2014 showed an average omission and commission errors of 67.1 and 54.4 . When using longer validation periods the errors were found smaller which indicates that the product is negatively influenced by temporal reporting accuracy . The inter comparison carried out with previous Fire cci versions and NASA s standard burned area product showed consistent spatial and temporal patterns . However the new algorithm estimated an average BA of 4.63 Mkm
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The algorithm is capable to detect burned area at 250m. The algorithm uses a two phase hybrid approach. The derived product detects more global burned area than other products. The derived product doubled burned area detection in boreal zones. The derived product improve sensitivity to detect small fires.
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S0034425719305139
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Quantifying the vertical distribution of atmospheric aerosols is crucial for estimating their impact on the Earth s energy budget and climate improving forecast of air pollution in cities and reducing biases in the retrieval of greenhouse gases from space . However to date passive remote sensing measurements have provided limited information about aerosol extinction profiles . In this study we propose the use of a spectral sorting approach to constrain the aerosol vertical structure using spectra of reflected sunlight absorption within the molecular oxygen O
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A spectral sorting approach is proposed for constraining aerosol profile from space. The approach is successfully applied to OCO 2 O. A band measurements. Retrieved profile parameters show good agreement with CALIPSO measurements. The approach can be used to map the aerosol vertical distribution on a global scale.
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S0034425719305152
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The Sudanian Savanna of West Africa is characterized by tropical savannas and woodlands . Accurate estimation of AGB and carbon stocks in this biome is important for addressing sustainable development goals as the information can aid natural resource management at varied spatial scales . Previous AGB mapping efforts focused on humid forests with little attention on savannas . This study explored the use of annual monthly time series of Senitinel 1 and Sentinel 2 data to map AGB in the SS . Backscatter spectral reflectance and derivatives were combined with field inventory data in a Random Forest regression to map AGB . Eight experiments were conducted with different data configurations to determine the potential of S 1 and S 2 for AGB mapping optimal image acquisition period for AGB mapping and contribution of image derivatives to improving the accuracy of AGB mapping . The predicted map was validated with 40 of the inventory data . Uncertainty in the AGB was assessed using mean absolute error root mean squared error coefficient of determination and symmetrical mean absolute percentage error . Results show that about 90 of the study area have low AGB stocks of less than 90Mg ha . Compared to S 1 S 2 achieved better prediction accuracy although combination of the two according to seasonality produced the best results . Images acquired in the dry season were found to be more useful for predicting AGB than those of rainy season . Also stress related vegetation indices and a red edge dependent normalized difference vegetation index not tested in previous AGB studies using Sentinels were found to be significant contributors to the superior performance of S 2 . Since biomass is a finite resource our results can provide valuable information on the sustainable use of biomass and energy security including studies on carbon cycling and ecosystem functions in the region . The demonstrated possibility of using open access earth observation data to map and monitor AGB in data scarce regions is useful and beneficial to attaining SDG indicators 15.2.1 and 15.3.1 . Further work on developing species specific wood densities and allometric equations is required to improve AGB and carbon stock estimation in the SS .
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Sentinel 2 found to be a better predictor of AGB than Sentinel 1. Combination of Sentinel 1 and 2 produce better results than either of them. Indices and biophysical parameters useful than spectral bands in AGB mapping. Dry season images achieve better results in AGB mapping than rainy season images. Open access satellite data can assist developing countries to attain SDG targets.
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S0034425719305164
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Satellite derived fire severity metrics are a foundational tool used to estimate fire effects at the landscape scale . Changes in surface characteristics permit reasonably accurate delineation between burned and unburned areas but variability in severity within burned areas is much more challenging to detect . Previous studies have relied primarily on categorical data to calibrate severity indices in terms of classification accuracy but this approach does not readily translate into an expected amount of error in terms of actual tree mortality . We addressed this issue by examining a dataset of 40 370 geolocated trees that burned in the 2013 California Rim Fire using 36 Landsat derived burn severity indices .
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Various spectral indices detect different aspects of fire related tree mortality. dNBR was not the best index but it was well suited for general use. Relativized versions of dNBR did not consistently improve performance. Range in observed mortality was as high as 40 around the predicted mean.
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S0034425719305188
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The development of metrics derived from LiDAR to quantify structural attributes of forests has contributed to substantial advances in wildlife habitat modeling . However further exploration of the numerous metrics available for quantifying canopy complexity could improve models of forest wildlife habitat while simultaneously increasing understanding of wildlife habitat relationships . We used the full set of metrics available in the LiDAR processing software FUSION including several structural metrics that have not previously been used in published habitat models to identify those that best quantify structural attributes associated with nest site occupancy by the Northern Spotted Owl NSO
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We investigated use of LiDAR metrics to improve habitat models for arboreal species. Maximum canopy height was the single best predictor of use by northern spotted owl. Additional 3D metrics separated structurally complex forest from unsuitable habitat. LiDAR metrics quantify ecologically important habitat features for arboreal species.
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S003442571930519X
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It has been widely reported that Arctic sea ice has decreased in both extent and thickness coupled with steadily rising mean annual temperatures . These trends have been particularly severe along the rock coast of southern Svalbard . Concerns have been raised over the potential for higher energy storms and longer ice free open water seasons to increase the exposure of Arctic coasts and consequently the concentration of infrastructure critical to Arctic community survival to enhanced rates of erosion . Here we present and apply innovative remote sensing monitoring and process analyses to assess the impact of recent coastal climatic changes . High resolution analyses demonstrate that the small scale 0.001m
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A decline cryogenic processes dominating over increased storm intensity. New 3D thermal signature mapping to visualise process zones. Arctic rock cliff sensitivity shown to both local and global processes. The efficacy of thermal processes have implications for strandflat development. Climatic signal assessed on process zones across eastern Spitsbergen.
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S0034425719305206
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Boreal forests constitute a large portion of the global forest area yet they are undersampled through field surveys and only a few remotely sensed data sources provide structural information wall to wall throughout the boreal domain . ArcticDEM is a collection of high resolution space borne stereogrammetric digital surface models covering the entire land area north of 60 of latitude . The free availability of ArcticDEM data offers new possibilities for aboveground biomass mapping across boreal forests and thus it is necessary to evaluate the potential for these data to map AGB over alternative open data sources . This study was performed over the entire land area of Norway north of 60 of latitude and the Norwegian national forest inventory was used as a source of field data composed of accurately geolocated field plots
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NFI data with ArcticDEM and Sentinel 2 used to model above ground biomass. Valuable synergy by combining ArcticDEM and Sentinel 2 data. ArcticDEM variables were more important than Sentinel 2 ones. Sentinel 2 data model was as accurate as ArcticDEM data model. Forest and terrain specific factors influenced the uncertainty and bias in model predictions.
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S0034425719305218
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Since 2010 SMOS retrievals of surface soil moisture and vegetation optical depth have been produced through the inversion of the so called Tau Omega vegetation emission model . Tau Omega is a 0
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Comparing 0. Tau Omega and 1. order Two Stream radiative transfer modelling. Similar performances of Tau Omega and 2S in retrieving SM and VOD at global scale. Slightly improved performances of 2S in retrieving SM in terms of. RMSD. Drier SM values by 0.015m. m. with 2S at global scale. Large Bias 0.1 between Tau Omega and 2S VOD retrievals over the tropical forests.
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S0034425719305280
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We present an analysis for Peru of the vertical accuracy and derived geomorphological parameters of three freely available Digital Elevation Models with 30 m grid sizes and one commercially available 12 m DEM ASTER GDEM2 SRTMv3.0 ALOS World 3D and 12 m TanDEM X . Their elevation values were compared against values measured with a dual frequency Trimble 5800 Global Navigation Satellite Systems receiver with two antennas in static relative positioning . A total of 139 ground control points with elevations of up to 4334m above sea level . were obtained from four topographically contrasting regions along the flat arid coast the semi dry Andes and the Amazon rainforest . The combined results of the four areas showed that the residuals of ASTER GDEM2 had a root mean square error of 6.907m SRTM3 5.113m and AW3D30 6.246m . For the two areas where TanDEM X was investigated a RMSE of 1.666m was obtained . When considering each area individually of the three 30 m DEMs SRTM3 performed best in all areas while ASTER GDEM2 was always performing worst . The standard deviation of the residuals of ASTER GDEM2 and AW3D30 varied much more between the four study areas than the SD of SRTM3 and TanDEM X . It was possible to establish linear correlations with R
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One of the few DEM comparison studies available for the South American continent. Centimetre precision ground control points of four contrasting areas in Peru. DEM elevation errors are in the order of metres less than officially reported. Correlations between DEM and GCP heights can be used to correct DEM values. Geomorphological and hydrological metrics show strengths and weaknesses of each DEM.
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S0034425719305292
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Artificial impervious areas are predominant indicators of human settlements . Timely accurate and frequent information on artificial impervious areas is critical to understanding the process of urbanization and land use cover change as well as of their impacts on the environment and biodiversity . Despite their importance there still lack annual maps of high resolution Global Artificial Impervious Areas with longer than 30 year records due to the high demand of high performance computation and the lack of effective mapping algorithms . In this paper we mapped annual GAIA from 1985 to 2018 using the full archive of 30 m resolution Landsat images on the Google Earth Engine platform . With ancillary datasets including the nighttime light data and the Sentinel 1 Synthetic Aperture Radar data we improved the performance of our previously developed algorithm in arid areas . We evaluated the GAIA data for 1985 1990 1995 2000 2005 2010 and 2015 and the mean overall accuracy is higher than 90 . A cross product comparison indicates the GAIA data are the only dataset spanning over 30 years . The temporal trend in GAIA agrees well with other datasets at the local regional and global scales . Our results indicate that the GAIA reached 797 076km
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We improved the performance of Exclusion Inclusion approach in arid regions. We mapped global artificial impervious areas GAIA with Google Earth Engine. The mean overall accuracy over multiple years is higher than 90 . GAIA reached 797 076km. by 2018 more than 2.5 times that of 1990. The top five countries are China US India Russia and Brazil.
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S0034425719305309
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Vegetation dynamics and phenology play an important role in inter annual vegetation changes in terrestrial ecosystems and are key indicators of climate vegetation interactions land use land cover changes and variation in year to year vegetation productivity . Satellite remote sensing data have been widely used for vegetation phenology monitoring over large geographic domains using various types of observations and methods over the past several decades . The goal of this paper is to present a detailed review of existing methods for phenology detection and emerging new techniques based on the analysis of time series multispectral remote sensing imagery . This paper summarizes the objective and applications of detecting general vegetation phenology stages often termed land surface phenology as well as more advanced methods that estimate species specific phenological stages . Common data processing methods such as data smoothing applied to prepare the time series remote sensing observations to be applied to phenological detection methods are presented . Specific land surface phenology detection methods as well as species specific phenology detection methods based on multispectral satellite data are then discussed . The impact of different error sources in the data on remote sensing based phenology detection are also discussed in detail as well as ways to reduce these uncertainties and errors . Joint analysis of multi scale observations ranging from satellite to more recent ground based sensors is helpful for us to understand satellite based phenology detection mechanism and extent phenology detection to regional scale in the future . Finally emerging opportunities to further advance remote sensing of phenology is presented that includes observations from Cubesats near surface observations such as PhenoCams and image data fusion techniques to improve the spatial resolution of time series image data sets needed for phenological characterization .
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Review of satellite remote sensing based land surface phenology detection methods. Discussion of advantages and drawbacks of phenological metrics extraction methods. Review of error sources and methods to reduce their effects on phenology detection. Opportunities and challenges related to improve phonological metrics extraction.
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S0034425719305334
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The thermal environment limits species ranges through its influence on physiology and resource distributions and thus affects species richness patterns over broad spatial scales . Understanding how temperature drives species richness patterns is particularly important in the context of global change and for effective conservation planning . Landsat 8 s Thermal Infrared Sensor allows direct mapping of temperature at moderate spatial resolutions overcoming limitations inherent in coarse interpolated weather station data that poorly capture fine scale temperature patterns over broad areas . TIRS data thus offer the unique opportunity to understand how the thermal environment influences species richness patterns . Our aim was to develop and assess the ability of TIRS based temperature metrics to predict patterns of winter bird richness across the conterminous United States during winter a period of marked temperature stress for birds . We used TIRS data from 2013 2018 to derive metrics of relative temperature and intra seasonal thermal heterogeneity . To quantify winter bird richness across the conterminous US we tabulated the richness only for resident bird species i.e . those species that do not move between the winter and breeding seasons from the North American Breeding Bird Survey the most extensive survey of birds in the US . We expected that relative temperature and thermal heterogeneity would have strong positive associations with winter bird richness because colder temperatures heighten temperature stress for birds and thermal heterogeneity is a proxy for thermal niches and potential thermal refugia that can support more species . We further expected that both the strength of the effects and the relative importance of these variables would be greater for species with greater climate sensitivity such as small bodied species and climate threatened species . Consistent with our predictions relative temperature and thermal heterogeneity strongly positively influenced winter bird richness patterns with statistical models explaining 37.3 of the variance in resident bird richness . Thermal heterogeneity was the strongest predictor of small bodied and climate threatened species in our models whereas relative temperature was the strongest predictor of large bodied and climate stable species . Our results demonstrate the important role that the thermal environment plays in governing winter bird richness patterns and highlight the previously underappreciated role that intra seasonal thermal heterogeneity may have in supporting high winter bird species richness . Our findings thus illustrate the exciting potential for TIRS data to guide conservation planning in an era of global change .
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Landsat 8 TIRS data are used to develop two new metrics of the thermal environment. Relative temperature and thermal heterogeneity predict winter bird richness. Thermal variables are more important for thermally sensitive species across the US. Thermal remote sensing data from TIRS have promise to guide conservation planning.
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S0034425719305346
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The quantification of vegetation height for the circumpolar Arctic tundra biome is of interest for a wide range of applications including biomass and habitat studies as well as permafrost modelling in the context of climate change . To date only indices from multispectral data have been used in these environments to address biomass and vegetation changes over time . The retrieval of vegetation height itself has not been attempted so far over larger areas . Synthetic Aperture Radar holds promise for canopy modeling over large extents but the high variability of near surface soil moisture during the snow free season is a major challenge for application of SAR in tundra for such a purpose . We hypothesized that tundra vegetation height can be derived from multispectral indices as well as from C band SAR data acquired in winter . To test our hypothesis we used C band SAR data from Sentinel 1 and multi spectral data from Sentinel 2 . Results show that vegetation height can be derived with an RMSE of 44cm from Normalized Difference Vegetation Index and 54cm from Tasseled Cap Wetness index . Retrieval from C band SAR shows similar performance but C VV is more suitable than C HH to derive vegetation height . An exponential relationship with
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Use of frozen condition backscatter allows vegetation height retrieval in tundra. C band SAR shows similar capabilities like multi spectral indices. The Tasseled Cap Wetness Index is specifically applicable in northern tundra. The evaluation across different regions suggests circumpolar applicability of C VV. Combination of Sentinel 1 and Sentinel 2 allows treatment of ambiguities.
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S003442571930536X
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The remote sensing of algal pigments is essential for understanding the temporal and spatial distribution of harmful algal blooms . In particular the vertical distribution of cyanobacterial pigment is critical factor in remote sensing because the diel vertical migration of cyanobacteria may affect the spectral signals according to observational time . Although numerous studies have been conducted on the remote sensing of algal bloom using pigments few studies considered the vertical distribution of the pigments for the remote sensing of cyanobacteria in inland waters . In this regard the objective of this study was to develop an improved bio optical remote sensing method using in situ remote sensing reflectance at different water depths and cumulative PC and Chlorophyll a concentrations which was cumulated from the surface to a 5 m water depth . The results showed that the bio optical algorithm using surface Rrs and surface pigment concentration was more accurate than that using the subsurface Rrs and surface pigments . The bio optical algorithm using subsurface Rrs showed the highest R squared R
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Cumulative pigment and subsurface Rrs were used to construct bio optical algorithms. Vertical cumulative pigment concentration was highly correlated with subsurface Rrs. PC map was developed using drone hyperspectral imagery and cumulative concentration. Relative abundance of PC was readily detectable by cumulative PC distribution map.
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S0034425719305371
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Satellite remote sensing of Land and Water Surface Temperature has many applications in studies of terrestrial and aquatic ecology . Retrieval of L WST requires a well calibrated radiometer and an accurate atmospheric correction . In the present study the performance of the Thermal InfraRed Sensor on board Landsat 8 is evaluated for the retrieval of L WST . libRadtran is used to retrieve atmospheric correction parameters based on atmospheric profiles of relative humidity and temperature from three global atmospheric models . Performance of single band retrievals is compared to typical MODTRAN results from the Atmospheric Correction Parameter Calculator and a split window approach . A multi temporal land masking method using imagery from the Operational Land Imager on board Landsat 8 is demonstrated and is used to automatically classify imagery in the matchup dataset in three classes of cloud cover . Two sources of in situ data covering the Belgian Coastal Zone are used for validation of the L WST product fixed locations in the Flemish Banks measurement network and underway data from regular RV Belgica campaigns . In the present study the single band methods outperformed the split window approach and consistent retrievals are found for the MODTRAN and libRadtran simulations . Typical single band surface temperature retrievals in quasi cloud free conditions have Root Mean Squared Differences of 0.7K and 1K for Bands 10 and 11 with low bias depending on the method and atmospheric profile source . For imagery with scattered clouds RMSD values increase to 1K and 2K respectively with an approximately 0.5K cold bias likely caused by cloud proximity . The calibration efforts combined into Collection 1 allows for accurate absolute surface temperature retrievals from B10 on Landsat 8 TIRS for homogeneous targets with known emissivity such as liquid water . The method is adapted to global processing and can be used for Land Surface Temperature retrieval with a suitable source of emissivity data .
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Landsat 8 TIRS Water surface temperature WST is derived using different methods. The open source libRadtran is found suitable for atmospheric correction of TIRS. In clear conditions the best performing WST product has RMSD 0.7K and MD 0.1K. Automated multi temporal land masking is performed for improved cloud screening. Full tile processing is supported LST can be estimated using emissivity data.
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S0034425719305383
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The planetary boundary layer height is an important parameter for understanding the accumulation of pollutants and the dynamics of the lower atmosphere . Lidar has been used for tracking the evolution of PBLH by using aerosol backscatter as a tracer assuming aerosol is generally well mixed in the PBL however the validity of this assumption actually varies with atmospheric stability . This is demonstrated here for stable boundary layers neutral boundary layers and convective boundary layers using an 8 year dataset of micropulse lidar and radiosonde measurements at the ARM Southern Great Plains and MPL at the GSFC site . Due to weak thermal convection and complex aerosol stratification traditional gradient and wavelet methods can have difficulty capturing the diurnal PBLH variations in the morning and forenoon as well as under stable conditions generally . A new method is developed that combines lidar measured aerosol backscatter with a stability dependent model of PBLH temporal variation . The latter helps recalibrate the PBLH in the presence of a residual aerosol layer that does not change in harmony with PBL diurnal variation . The hybrid method offers significantly improved PBLH detection with better correlation and smaller biases under most thermodynamic conditions especially for SBL and CBL . Relying on the physical process of PBL diurnal development different schemes are developed for growing maintenance and decaying periods . Comprehensive evaluation of this new method shows much better tracking of diurnal PBLH variation and significantly smaller biases under various pollution levels .
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A lidar based algorithm retrieving planetary boundary layer height was developed. This method was evaluated in detail under various thermodynamic stabilities. This method showed a great improvement for the stable boundary layer. The biases were largely reduced under various stabilities and pollution levels.
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S0034425719305395
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Tree canopy density metrics derived from airborne lidar data are used in a range of crucial environmental monitoring forestry and natural resource management applications . The derivation of spatially and temporally consistent TCDM however typically requires field calibration to account for differences in instrument survey parameters . Lidar surveys with no coincident field measurements consequently will have an unknown error associated with TCDM limiting their application . In this study we analysed an extensive set of lidar captures with coincident field data to determine the lidar TCDM that best match the canopy gap probability
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An extensive dataset of field plots and airborne lidar data was collated. The effect of lidar parameters on canopy density metrics could not be modelled. Standard canopy density metrics matched field measurements with low RMSE 7 .
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S0034425719305401
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Mapping and monitoring of indicators of soil cover vegetation structure and various native and non native species is a critical aspect of rangeland management . With the advancement in satellite imagery as well as cloud storage and computing the capability now exists to conduct planetary scale analysis including mapping of rangeland indicators . Combined with recent investments in the collection of large amounts of in situ data in the western U.S. new approaches using machine learning can enable prediction of surface conditions at times and places when no in situ data are available . However little analysis has yet been done on how the temporal relevancy of training data influences model performance . Here we have leveraged the Google Earth Engine platform and a machine learning algorithm to identify the potential impact of different sampling times on estimation of rangeland indicators from the Bureau of Land Management s Assessment Inventory and Monitoring and Landscape Monitoring Framework programs . Our results indicate that temporally relevant training data improves predictions though the training data need not be from the exact same month and year for a prediction to be temporally relevant . Moreover inclusion of training data from the time when predictions are desired leads to lower prediction error but the addition of training data from other times does not contribute to overall model error . Using all of the available training data can lead to biases toward the mean for times when indicator values are especially high or low . However for mapping purposes limiting training data to just the time when predictions are desired can lead to poor predictions of values outside the spatial range of the training data for that period . We conclude that the best Random Forest prediction maps will use training data from all possible times with the understanding that estimates at the extremes will be biased .
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We used Google Earth Engine GEE to process large volume of remotely sensed data. We compared different machine learning algorithms in modeling rangeland indicators. We have shown temporal relevance is the key to modeling rangeland indicators.
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S0034425719305413
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2019 is the 50th anniversary of Remote Sensing of Environment . RSE serves the Earth observation community with the publication of results on the theory science applications and technology of remote sensing . Thoroughly interdisciplinary it publishes state of the art papers on terrestrial oceanic marine and atmospheric sensing . The emphasis of the journal is on biophysical and quantitative approaches to remote sensing at local to global scales . The 7 800 papers it has published have been cited more than 520 000 times and it has consistently had the highest journal impact factor since 1983 . This paper summarizes RSE s history and publication metrics and discusses the philosophy approach and contributions that have made it the leading remote sensing journal for many years .
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2019 is the 50th anniversary of Remote Sensing of Environment. Publishes on the theory science applications and technology of remote sensing. Biophysical quantitative research at local to global scales. Review of History philosophy approach contributions and publication metrics. Leading remote sensing journal with 520 000 citations of 7 800 papers.
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S0034425719305425
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This short communication concerns errors in the albedo computation from Sentinel 2 in the article by S. Vanino et al . Capability of Sentinel 2 data for estimating maximum evapotranspiration and irrigation requirements for tomato crop in Central Italy Remote Sensing of Environment vol . 215 2018 Pag . 452470
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Comments about doubtful albedo computation in the article by S. Vanino et al. Errors on the weight computation for Sentinel 2 Table 3 of the article . A revision on the weighting coefficients computation is needed.
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