Making Existing Surface Albedo Products Compatible with the Needs of Land Surface Models

Improving the estimates of the radiation fluxes in particular and energy budget in general over continental surfaces requires the assimilation of relevant and measurable variables responding to the various types of forcings that can be experienced by land-surfaces. Surface albedo is one such variable controlling the net radiation fluxes which can themselves also be estimated from space-borne sensors. Albedo products are nowadays delivered routinely by various space agencies. However, the word "surface albedo" covers various meanings depending on the level of sophistication adopted to account for the coupling between the bidirectional properties of the surface and the diffuse irradiance available at the bottom of the atmosphere. This state of affairs renders the use and intercomparison of these albedo products more difficult than would appear at first sight.This presentation will first describe albedo as a problem involving the radiative coupling of the surface and the atmosphere, and then illustrate the relationships linking the various albedo products currently available from various instruments. Once established, such relationships allow to intercompare surface albedo products from MODIS, MISR and Meteosat. Preliminary results in this direction will be shown. These efforts should prove useful to bridge the gap between the remote sensing derived products and the modeling needs of the climate and hydrology community.