HR: 08:15h
AN: H21I-02 INVITED     [Abstracts]
TI: Temporal changes in continental water storage from GRACE observations
AU: * CAZENAVE, A
EM: anny.cazenave@cnes.fr
AF: LEGOS, 14 Avenue Edouard Belin, TOULOUSE, 31400 France
AU: RAMILLIEN, G
EM: guillaume.ramillien@notos.cst.cnes.fr
AF: LEGOS, 14 Avenue Edouard Belin, TOULOUSE, 31400 France
AB: We present results on land hydrology based on the inversion of monthly GRACE geoids spanning over a 2-year period (mid-2002 to mid-2004).The method of separation we have developed is based on generalized least-squares inversion (Ramillien et al., 2004). It consists of solving for `water height equivalent' spherical harmonic coefficients of four separate fluid reservoirs (atmosphere, ocean, soil waters and snow) after inverting the observed geoid coefficients (expressed in terms of time-variable anomalies with respect to a mean reference geoid) and using global hydrological model outputs as constrainsts. A cutoff at degree 30 (half-wavelenth of 650 km) is considered. The solutions are compared to two global hydrological models : the Land Dynamics model (Milly and Shmakin, 2002) and the Watergap Global Hydrology model (Doll et al, 2003). The monthly GRACE solutions for total land waters (sum of soil water, including underground waters, plus snow) show patterns in rather good agreement with the models, especially at the seasonal frequency. The strongest signal is observed in large tropical river basins (Amazon basin in South America, Congo and Niger basins in Africa, Ganges and Bramhapoutra basin in North Western India, etc.), as well as in Northeast America, and Western Asia (Volga basin) and Central Asia (Ob and Lena basins). In these northern hemisphere regions, the observed signal results from the combined contributions of total soil water and snow. In terms of relative amplitude, the solution differs significantly from the models however, as do the models each other.
DE: 1800 HYDROLOGY
DE: 1833 Hydroclimatology
DE: 1836 Hydrologic budget (1655)
DE: 1866 Soil moisture
DE: 1655 Water cycles (1836)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting