NRT Product Available since Feb 2009
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.
This operational product is documented in the following documents:
Please see Product Peer-Review publications in References.
The use of LSA SAF products in publications is kindly requested to be duly acknowledged:
MTAL albedo data were 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 Albedo product is generated each 10 days at the full spatial resolution of the MSG/SEVIRI instrument. An iterative scheme allows the composition of the information with a characteristic time scale of 31 days. MTAL filename date refers to the central date of the 31 days period.
The product is based on the three short-wave channels (VIS 0.6 µm, NIR 0.8 µm, SWIR 1.6 µm). In addition to the corresponding narrowband estimates, broadband albedo is derived for the visible, near-infrared and total short-wave wavelength ranges. Information on cloud cover is obtained from the output of the Nowcasting and Very Short Range Forecasting Satellite Application Facility (NWC SAF) software. Dynamic information on the atmospheric pressure and water vapour content comes from the ECMWF numerical weather prediction model. Climatological values are currently used for ozone concentration and aerosol optical thickness.
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 MTAL albedo product is computed on a ten-daily basis within the area covered by the MSG disk. For each release, 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 20%. 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).
Rahman, H., & Dedieu, G. (1994). SMAC: a simplified method for the atmospheric correction of satellite measurements in the solar spectrum. Remote Sensing, 15(1), 123-143.