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Land surface albedo is a key variable for characterising the energy balance in the coupled soil-vegetation-atmosphere system. The albedo quantifies the part of the energy that is absorbed and transformed into heat and latent fluxes. Owing to strong feedback effects the knowledge of albedo is important for determining weather conditions at the atmospheric boundary layer. Climate sensitivity studies with Global Circulation Models have confirmed the unsteady nature of the energy balance with respect to small changes in surface albedo. Other domains of applications are in hydro-meteorology, agro-meteorology and environment-related studies.
The characteristics and file format of this demonstration Data Record are the same as its correspondent NRT product. Thus documented by the common Algorithm Theoretical Basis Document (ATBD), Product User Manual document (PUM) and Product Output Format document (POF) documents. The validation results for this Data Record are available in the (VR) document.
Please see Product Peer-Review publications in References.
The use of LSA SAF products in publications is kindly requested to be duly acknowledged:
MTAL-R albedo was provided by the EUMETSAT Satellite Application Facility on Land Surface Analysis (LSA SAF; Trigo et al., 2011)
Trigo, I. F., C. C. DaCamara, P. Viterbo, J.-L. Roujean, F. Olesen, C. Barroso, F. Camacho-de Coca, D. Carrer, S. C. Freitas, J. García-Haro, B. Geiger, F. Gellens-Meulenberghs, N. Ghilain, J. Meliá, L. Pessanha, N. Siljamo, and A. Arboleda, 2011: The Satellite Application Facility on Land Surface Analysis. Int. J. Remote Sens., 32, 2725-2744, doi: 10.1080/01431161003743199
The MSG mission in operations since 2004) already provides a relatively long time series of VIS and IR observations over the full Earth Disk centred at 0º. The full archive of MSG/SEVIRI data was reprocessed to provide the user community a consistent, homogeneous and continuous Data Record of the 10-day Surface Albedo (MTAL) for the period 2004-2015.
The CDR thus uses consolidated (reanalysed) estimates of atmospheric composition: ozone, water vapour and atmospheric pressure (source ECMWF), as well as the most up to date cloud masks (source NWC SAF/EUMETSAT).
In addition to exploit reanalysed input data, this Data Record was obtained with the best and latest version of its equivalent NRT product (MTAL, LSA_102 product) algorithm, which complements the time series from 2016 onwards.
In a first step the cloud-free reflectance observations of each slot are corrected for atmospheric effects using the simplified radiative transfer code SMAC (Rahman and Dedieu, 1994). Afterwards, the linear kernel-driven BRDF model from Roujean et al. (1992) is fitted to a daily time series of the resulting top-of-canopy reflectance factor values. In the applied model the reflectance properties are split into two kernels describing the dominant light scattering processes in separating geometric and volumetric scattering effects, either interpreted as a transposition of scaling effects, a separation between the soil and vegetation, or the conjunction between thin and thick optical media. Albedo estimates are then obtained by suitably integrating the BRDF model functions. Generated products are the directional-hemispherical (or "black-sky") albedo at local solar noon and for the narrowband and total broadband range also the bi-hemispherical (or "white-sky") albedo.
The Albedo product is computed on a daily basis within the area covered by the MSG disk. For each day the albedo quantities, their respective error estimates, and a processing flag are disseminated in HDF5 format. The relevant information concerning the data fields is included in the HDF5 attributes.
For each albedo quantity the algorithm delivers theoretical estimates for the non-correlated (random) error contribution by propagating estimates for the error of the top-of-canopy reflectance factors through the linear model inversion. In practice non-detected clouds and systematic errors in the aerosol optical thickness values used for the atmospheric correction are the most important error sources. The specification for the overall accuracy of the albedo product is 10%. Results of detailed validation studies are given in the Validation Report.
Carrer, D.; Moparthy, S.; Lellouch, G.; Ceamanos, X.; Pinault, F.; Freitas, S.C.; Trigo, I.F. Land Surface Albedo Derived on a Ten Daily Basis from Meteosat Second Generation Observations: The NRT and Climate Data Record Collections from the EUMETSAT LSA SAF. Remote Sens., 10, 1262 (2018).
Carrer, D., Smets, B., Ceamanos, X., RoujeanW. H. , J.-L., and R. Lacaze (2018), ‘Copernicus Global Land SPOT/VEGETATION and PROBA-V surface albedo products - 1km Version 1’, Algorithm Theoretical Basis Document, Issue 2.11, Copernicus Global Land Operations “Vegetation and Energy” ”CGLOPS-1”, Framework Service Contract N° 199494 (JRC).
Carrer, D., Roujean, J.-L. & Meurey, C. Comparing operational MSG/SEVIRI land surface albedo products from Land SAF with ground measurements and MODIS. IEEE Transactions on Geoscience and Remote Sensing 48, 1714–1728 (2010).
Geiger, B., Carrer, D., Franchisteguy, L., Roujean, J.-L. & Meurey, C. Land surface albedo derived on a daily basis from Meteosat second generation observations. IEEE Transactions on Geoscience and Remote Sensing 46, 3841–3856 (2008).
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