Satellite Altimetry from Topex-Poseidon is used to estimate the annual variation of the global sea level. This observed signal, corrected for steric effects, can give the seasonal variations of soil moisture and snow mass over continents. These observations can be used to study the realism of the soil moisture simulations in General Circulation Models.

A new land surface scheme, Orchidee, has been developed at the Institute Pierre Simon Laplace. It has been integrated in an off-line mode and coupled to the LMD atmospheric General Circulation Model. The soil moisture content and snow mass simulated by these integrations are compared to observations.

We analyse the importance of different regions or catchment basins to the global signal; the role of each water flux simulated by Orchidee in determining the range of annual soil moisture variation; the interannual variability of soil moisture content simulated by the LMD GCM.