Microwave land surface emissivities have been calculated over the globe for ~10 yr between 19 and 85 GHz at 53° incidence angle for both orthogonal polarizations, using satellite observations from the Special Sensor Microwave Imager (SSM/I). Ancillary data (IR satellite observations and meteorological reanalysis) help remove the contribution from the atmosphere, clouds, and rain from the measured satellite signal and separate surface temperature from emissivity variations. The method to calculate the emissivity is general and can be applied to other sensors. The monthly mean emissivities are available for the community, with a 0.25° × 0.25° spatial resolution.

The emissivities are sensitive to variations of the vegetation density, the soil moisture, the presence of standing water at the surface, or the snow behavior, and can help characterize the land surface properties.

These emissivities (not illustrated in this paper) also allow for improved atmospheric retrieval over land and can help evaluate land surface emissivity models at global scales.

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Centre National de la Recherche Scientifique, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris, Paris, France

Centre National de la Recherche Scientifique/L'lnstitut Pierre-Simon Laplace, Laboratoire de Météorologie Dynamique, University Paris VI, Paris, France

NASA Goddard Institute for Space Studies, New York, New York.