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This study examines the impact of daily satellite-derived albedos on short-range forecasts in a limited-area numerical weather prediction (NWP) model over Europe. Contrary to previous studies in which satellite products were used to... more
This study examines the impact of daily satellite-derived albedos on short-range forecasts in a limited-area numerical weather prediction (NWP) model over Europe. Contrary to previous studies in which satellite products were used to derive monthly “climatologies,” a daily surface (snow free) albedo is analyzed by a Kalman filter. The filter combines optimally a satellite product derived from the Meteosat Second Generation geostationary satellite [and produced by the Land Surface Analyses–Satellite Application Facility of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT)], an albedo climatology, and a priori information given by “persistence.” The surface albedo analyzed for a given day is used as boundary conditions of the NWP model to run forecasts starting the following day. Results from short-range forecasts over a 1-yr period reveal the capacity of satellite information to reduce model biases and RMSE in screen-level temperature (during dayti...
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ABSTRACT Vegetation surfaces play an important role in the Earth's energy balance and have a significant impact on the global carbon cycle. The fraction of solar radiation that is absorbed by a vegetation canopy will assess the... more
ABSTRACT Vegetation surfaces play an important role in the Earth's energy balance and have a significant impact on the global carbon cycle. The fraction of solar radiation that is absorbed by a vegetation canopy will assess the rate of photosynthesis and besides the amount of carbon flux further fixed or released by this same canopy layer. The radiative transfer scheme within the canopy of ISBA-Ags interactive vegetation model was defined in 1998 by Calvet et al [2] according to a self-shading approach. The incident fluxes at the top of the canopy go through a multilayer vegetation cover. Then, the attenuated flux in the PAR wavelength domain of each layer is used by the Jacobs Model [3] to evaluate the net assimilation (An) of the leaf. Net assimilation of the leaf estimated for each layer is mixed together to derive the average An quantity of the total vegetation cover. A detailed description of the vegetation radiative transfer scheme within the canopy is given in Appendix B of Calvet et al. [2]. The objective of the present study is the improvement of the current scheme and its evaluation. The impact of the new absorbed radiation on the photosynthesis module is considered, in order to obtain better simulations of the Leaf Area Index (LAI) and Gross Primary Production (GPP). These evaluations sustain the value added of an advanced representation of the radiative transfer within the canopy in order to estimate the photosynthesis.
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International audienceNine French public institutions involved in Earth Observation, environmental studies and scientific research (CEA, CNES, Cirad, CNRS, IGN, INRA, IRD, Irstea and Météo-France), have launched in 2012 the Theia Land... more
International audienceNine French public institutions involved in Earth Observation, environmental studies and scientific research (CEA, CNES, Cirad, CNRS, IGN, INRA, IRD, Irstea and Météo-France), have launched in 2012 the Theia Land Data Centre, pooling their expertise and resources to make satellite data available to the environmental research community and to public policy actors. The Theia primary mission is (i) to build a national space data infrastructure able to produce value-added space data over land and provide services fitted to users’ needs, (ii) to support the sharing of experience and scientific knowledge on methodologies relevant to process and use space data for land thematic issues. To this end, Theia is working to produce data, products, methods and services linked to space observations of continental areas, from local (ecosystem and territory) to global scale, and make them available to the user community. It is backed up by a distributed spatial data infrastructure (SDI), and by scientific expertise hubs in various regions. The SDI links Montpellier (GEOSUD at Maison de la Télédétection) and Toulouse (CNES supported by the CESBIO laboratory, and IGN). The SDI provides already through its portal (www.theia-land.fr) a number of satellite products : yearly coverages at high resolution over the French territory with Spot and Rapid Eye, results from the Take 5 – Spot 4 experiment over 45 sites wordwide from February to June 2013 to simulate Sentinel-2 imagery, time series of orthorectified, atmospherically corrected Landsat data over France. Much more is to come : a first batch of 100 000 images over areas worldwide from the Spot World Heritage programme, provided free of charge for non commercial users, time series of river and lakes height worldwide, atmospherically corrected and monthly composites of Sentinel-2 data over an area equivalent to that of Europe, a new climate record of vegetal variables at global scale with AVHRR, and others. The organisation of science expertise hubs at national level has been initiated. A number of science teams have been created with the goal to prepare processing lines of value added satellite products, in particular from the Sentinel satellites, such as land cover, watered areas, snow areas, imperviousness areas, albedo, vegetal variables at decametric scale, water quality and height, and others
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Satellite Sentinel-2 offers a global coverage of the Earth at the frequency of a few days with pixel size ranging from 10 to 20 meters. Such spatio-temporal resolution fosters an advanced research in agriculture. Accounting for BRDF... more
Satellite Sentinel-2 offers a global coverage of the Earth at the frequency of a few days with pixel size ranging from 10 to 20 meters. Such spatio-temporal resolution fosters an advanced research in agriculture. Accounting for BRDF (Bidirectional Reflectance Distribution Function) information is required both for target monitoring and surface albedo estimate. BRDF sampling being limited from HR (High Resolution) sensors, the added-value of the BRDF 300m from PROBA-V instrument is assessed. Results are shown for the seasonal cycles 2016 and 2017 using parameterized and detailed radiation transfer models. The validation is carried on for anchor ICOS (Integrated Carbon Observation System) stations located on the French territory.
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Geography, Computer Science, Algorithms, Remote Sensing, Global change, and 14 moreLandscapes, Land Cover, Classification, Projection, Geomatic Engineering, Quality assessment, Accuracy, Spatial Distribution, Spatial resolution, Accuracy Assessment, Precision, Land Cover Mapping, Pixel, and Image Acquisition
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Earth Sciences, Environmental Science, Biological Sciences, Atmospheric sciences, Soil moisture, and 13 moreTropical forest, Soil Vegetation Atmosphere Transfer Modeling, Life Expectancy, Leaf Area Index, Vegetation Cover, Evergreen, Growth Model, Leaf Area, Atmospheric Carbon Dioxide, Soil Water, Water budget, Stomatal Conductance, and Model test
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Environmental Science, Geophysics, Water Cycle, Atmospheric sciences, Soil moisture, and 12 moreEvapotranspiration, Surface Water, Soil Vegetation Atmosphere Transfer Modeling, Field Experiment, Soil Temperature, Annual Cycle, Annales, Water Content, Energy Flux, Field Data, Water budget, and Continuous time
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<p>Land surface temperature (LST) is the direct driving force of turbulent heat fluxes at the surface... more
<p>Land surface temperature (LST) is the direct driving force of turbulent heat fluxes at the surface and atmosphere interface and is widely used in the fields of evapotranspiration estimation (Su et al., 2002) and energy budget (Liang et al., 2019). Remote sensing products offer the only possibility for measuring LST with completely spatially averaged values. The thermal radiation directionality (TRD) effect has been widely concerned in the area of thermal infrared (TIR) remote sensing over 50 years which can lead to the directional brightness temperature (DBT) difference between different viewing directions up to 10 K (Cao et al., 2019). Many models have been proposed to simulate the DBT patterns over different underlying surfaces aimed to achieve the TRD effect correction for the satellite LST products. In practice, it is advised to handle only TRD models having a limited number of input parameters for operational normalization of LST products. The use of TIR kernel-driven models appears a good tradeoff between physical accuracy and operationality. It remains that the existing 4 TIR kernel-driven models (Ross-Li, LSF-Li, Vinnikov, RL) underestimate the hotspot effect, especially for continuous canopies. In this study, a new general framework of TIR kernel-driven modeling is proposed to overcome such issue. It is a linear combination of three kernels (including a base shape kernel, a hotspot kernel and an isotropic kernel) with the ability to simulate the bowl, dome and bell shapes in the solar principal plane. 4 specific models (Vinnikov-RL, LSF-RL, Vinnikov-Chen, LSF-Chen) within the new framework were further developed to assess their fitting abilities for both continuous and discrete vegetation canopies. To evaluate 4 existing models and 4 new models comprehensively, it was prepared 102 groups of 4SAIL/DART generated multi-angle datasets considering 6 different canopy architectures and 17 component temperatures. Results show that the 4 new models behave slightly better than the 4 existing models over discrete canopies (R2 increases from 0.791~0.989 to 0.976~0.996) whereas they significantly improved the fitting accuracy over continuous canopies (R2 increases from 0.661~0.970 to 0.940~0.997). The innovative new general framework with three kernels and four parameters improve the fitting ability significantly since the addition of one more degree of freedom. This new kernel-driven modeling framework is a potential tool to achieve angular correction of LST products.</p>
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Surface upward longwave radiation (SULR) is one of the four components of the surface radiation budget, which is defined as the total surface upward radiative flux in the spectral domain of 4-100 μm. The SULR is an indicator of surface... more
Surface upward longwave radiation (SULR) is one of the four components of the surface radiation budget, which is defined as the total surface upward radiative flux in the spectral domain of 4-100 μm. The SULR is an indicator of surface thermal conditions and greatly impacts weather, climate, and phenology. Big Earth data derived from satellite remote sensing have been an important tool for studying earth science. The Advanced Baseline Imager (ABI) onboard the Geostationary Operational Environmental Satellite (GOES-16) has greatly improved temporal and spectral resolution compared to the imager sensor of the previous GOES series and is a good data source for the generation of high spatiotemporal resolution SULR. In this study, based on the hybrid SULR estimation method and an upper hemisphere correction method for the SULR dataset, we developed a regional clear-sky land SULR dataset for GOES-16 with a half-hourly resolution for the period from 1st January 2018 to 30th June 2020. The ...
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Surface upward longwave radiation (SULR) is a critical component in the calculation of the Earth’s surface radiation budget. Multiple clear-sky SULR estimation methods have been developed for high-spatial resolution satellite... more
Surface upward longwave radiation (SULR) is a critical component in the calculation of the Earth’s surface radiation budget. Multiple clear-sky SULR estimation methods have been developed for high-spatial resolution satellite observations. Here, we comprehensively evaluated six SULR estimation methods, including the temperature-emissivity physical methods with the input of the MYD11/MYD21 (TE-MYD11/TE-MYD21), the hybrid methods with top-of-atmosphere (TOA) linear/nonlinear/artificial neural network regressions (TOA-LIN/TOA-NLIN/TOA-ANN), and the hybrid method with bottom-of-atmosphere (BOA) linear regression (BOA-LIN). The recently released MYD21 product and the BOA-LIN—a newly developed method that considers the spatial heterogeneity of the atmosphere—is used initially to estimate SULR. In addition, the four hybrid methods were compared with simulated datasets. All the six methods were evaluated using the Moderate Resolution Imaging Spectroradiometer (MODIS) products and the Surfac...
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ABSTRACT In this paper, we present an operational procedure for the inversion of kernel-driven bi-directional reflectance distribution function (BRDF) model and further albedo retrieval to be applicable to the SEVIRI/MSG reflectance... more
ABSTRACT In this paper, we present an operational procedure for the inversion of kernel-driven bi-directional reflectance distribution function (BRDF) model and further albedo retrieval to be applicable to the SEVIRI/MSG reflectance measurements. Our approach aims at bringing solutions to an ill-posed problem that is when the ratio of extreme eigenvalues of the inverse matrix is of several orders of magnitude due to sparse and irregular angular samplings. The geometric Li-Sparse reciprocal and Roujean kernels are considered in the procedure applied to space-borne Polarization and Directionality of Earth Reflectance (POLDER) sensor data which decomposes as follows: (1) quality control, (2) accumulation of a priori information on model coefficients of directional hemispherical reflectance, and (3) implementation of BRDF model inversion methods based on the biased estimation instead of usual nonbiased least solution due to its large variance. The first two steps are detailed in this paper; the third one appears in a companion paper. The data control procedure consists both in filtering inputs of reflectance data and output of model coefficients. In the first stage, the analysis criteria rely on Fisher statistics. In the second stage, a procedure is applied to red and near-infrared POLDER data corresponding to the 16 classes of International Geosphere Biosphere Program (IGBP) land cover classification. Among the retained criteria, some are based on the BRDF shape. They encompass (1) T-statistics, (2) the bowl shape index (BSI), (3) the dome shape index (DSI), (4) the white sky albedo (WSA, bi-hemispherical reflectance), and (5) the black sky albedo variance (BSA, directional–hemispherical reflectance). Statistical results include mean values and covariance matrix for the spectral BRDF model coefficients. This procedure eliminates about 10% of data measurements, thereby reducing uncertainty in retrieved BRDF model coefficients and WSA.
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The land surface albedo is a key parameter influencing the climate near the ground. Therefore, it must be determined with sufficient accuracy. In this paper, a statistical inversion method is presented in support of the application of... more
The land surface albedo is a key parameter influencing the climate near the ground. Therefore, it must be determined with sufficient accuracy. In this paper, a statistical inversion method is presented in support of the application of kernel-based Bi-directional Reflectance Distribution Function (BRDF) models for the calculation of the surface albedo. The method provides the best linear unbiased estimations (BLUE) of the BRDF model coefficients for an arbitrary number of available angular measurements. When the number of measurements exceeds the number of the estimated coefficients, the QR decomposition method is proposed to improve the ill-conditional features of the inversion matrix. In other cases, the singular value decomposition (SVD) method is suggested. The proposed inversion method is innovative in that it provides confidence intervals for each of the BRDF model coefficients with a prescribed significance expressed by a probability level. Five candidate kernel-driven BRDF models were used in the present simulation study: Li–Sparse, Roujean, Li–Sparse–Wanner, Li–Dense and Walthall. A ground-based reflectance measurement data set including 11 surface types forms the background for the inversion experiments. The results show a strong dependence on the solar zenith angle (SZA) and on the land cover type (LCT) for all candidate models. Owing to this, none model could be recommend in a general manner. The Li–Sparse and the Li–Sparse–Wanner models performed the best for the grass and wheat LCT, while the Roujean model appeared as a favorite for the pine and deciduous forests. The implementation of the confidence interval technique shows that the BRDF model coefficients can be retrieved with an uncertainty of 20–30%, and somewhat greater in the case of forest. The measured angular reflectance curves lie, as a rule, within the uncertainty bands related to the 5% significance level (95% probability). The corresponding albedo estimates can be characterized by an absolute uncertainty of 1–2% in the visible band and 5–10% in the near infrared band, or by 10–30% in relative terms. The reflectance measurements at low SZA values are preferable for BRDF model inversion for the grassland and crop, while medium range of SZA seems to provide more information on forest features. For the majority of LCT, the results of BRDF model inversion seem to be less reliable when considering multi-angular measurements for various SZA than for a single SZA.
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Mathematics, Remote Sensing, Experimental Design, Near Infrared, Low Noise Measurement Systems, and 15 moreLand Cover, Performance Model, Geomatic Engineering, Convergence Rate, Remote Sensing of the Nearshore Environment, Inverse Method, Random Noise, Optimal Design, Deciduous Forest, Confidence Interval, QR Decomposition, model comparison, Distribution Function, Residual, and Model performance
The European continent is influenced by different types of aerosols transported from Africa, Asia, North America or by volcanic aerosols. Regional emissions are responsible for most aerosol concentrations that exceed air quality... more
The European continent is influenced by different types of aerosols transported from Africa, Asia, North America or by volcanic aerosols. Regional emissions are responsible for most aerosol concentrations that exceed air quality standards, but emissions and long-range transport at a global scale can lead to episodic peaks in concentrations. Our research deals with the improvement of different parameterisation schemes implemented in the chemical transport model of Météo-France MOCAGE. Such improvements are necessary to assess the importance of long-range in respect to short and medium-range transport concerning the aerosol quantities and spatial distribution and to see how episodic events of high aerosol concentrations (volcanic eruptions or desert dust outbreaks) impact the air quality over Europe. An attention is given to the importance of emissions, forcing and particularly deposition processes. Different schemes of in-cloud scavenging and below-cloud scavenging (by rain and snow)...
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ABSTRACT This article presents a new aerosol optical depth (AOD) product delivered in near real time by the ICARE Data and Services Center to the scientific community. The AERUS-GEO (Aerosol and surface albEdo Retrieval Using a... more
ABSTRACT This article presents a new aerosol optical depth (AOD) product delivered in near real time by the ICARE Data and Services Center to the scientific community. The AERUS-GEO (Aerosol and surface albEdo Retrieval Using a directional Splitting method - application to GEOstationary data) product is derived from observations from the Meteosat Second Generation (MSG) geostationary satellite covering Europe, Africa, and part of Asia and South America. The retrieval method exploits the directional information contained in the series of 96 MSG observations per day of the Earth's disk to derive a daily averaged AOD. The performances of this product are similar to those of other widely used satellite-derived AOD. This article illustrates the advantages of the spatial (3 km at best) and temporal (daily) resolution of the AERUS-GEO product to monitor particular aerosol activity (e.g., volcanic eruptions) or to study given phenomena (e.g., the impact of topography on aerosol loading).
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Information related to land surface is immensely important to global change science. For example, land surface changes can alter regional climate through its effects on fluxes of water, energy, and carbon. In the past decades, data... more
Information related to land surface is immensely important to global change science. For example, land surface changes can alter regional climate through its effects on fluxes of water, energy, and carbon. In the past decades, data sources and methodologies for characterizing land surface heterogeneity (e.g., land cover, leaf area index, fractional vegetation cover, bare soil, and vegetation albedos) from remote sensing have evolved rapidly. The double ECOCLIMAP database—constituted of a land cover map and land surface variables and derived from Advanced Very High Resolution Radiometer (AVHRR) observations acquired between April 1992 and March 1993—was developed to support investigations that require information related to spatiotemporal dynamics of land surface. Here is the description of ECOCLIMAP-II: a new characterization of the land surface heterogeneity based on the latest generation of sensors, which represents an update of the ECOCLIMAP-I database over Africa. Owing to the m...