Evolution of high-latitude snow mass derived from the GRACE gravimetry mission (2002-2004)

Since March 2002, the GRACE mission provides monthly global maps of geoid time-variations. These new data carry information on the continental water storage, including snow mass variations, with a ground resolution of similar to 600 - 700 km. We have computed monthly snow mass solutions from the inversion of the 22 GRACE geoids (04/2002 - 05/2004). The inverse approach developed here allows to separate the soil waters from snow signal. These snow mass solutions are further compared to predictions from three global land surface models and snow depths derived from satellite microwave data. We find that the GRACE solutions correlate well with the high-latitude zones of strong accumulation of snow. Regional means computed for four large boreal basins (Yenisey, Ob, Mac Kenzie and Yukon) show a good agreement at seasonal scale between the snow mass solutions and model predictions (global rms similar to 30 - 40 mm of equivalent-water height and similar to 10 - 20 mm regionally).