Detection of Global Water Storage Variation Using Grace

Abstract

Global water storage variations on the land and in the ocean are recovered by using GRACE monthly time-variable gravity fields, and these results are compared with land hydrological data, satellite altimeter data and oceanic model solutions. Comparing the gravity variation at SOURE station calculated by land water storage variation with the solution from GRACE gravity field coefficients truncated to degree and order 15, we find both are close to one another with an evident annually varying term. In the Amazon drainage basin, for a 106m smoothing radius and GRACE gravity field coefficients truncated to degree and order 15, the annual amplitude of average water storage variation thickness is about 15.6×10−2m, smaller than 23.7×10−2m for a 4×105m smoothing radius. When we study the water storage variation in the Yangtze drainage basin, we expand the hydrological data in spherical harmonic coefficients, and dispose them of truncation and smoothness as same as GRACE data. The result indicates that the average thickness of water storage variation measured from GRACE agrees well with the hydrological data solution. For the range of latitudes –66 to 66 degree in the ocean, the seawater mass variation recovered from GRACE is in good agreement with the result from satellite altimeter combined with the oceanic model, but for the 2°×2° every grid, there exist considerable differences in some grid regions, and the largest is over 0.2m, the RMS is 3.8×10−2m. So the GRACE satellite time-variable gravity field can only determine water storage variation over thousands kilometers or more with high accuracy presently.