干旱区生态环境知识资源中心

This paper is devoted to the problem of the ground-satellite comparison of time-variable gravity. We first review the different methods used to validate satellite gravity observations (ground truth experiment) and point out possible issues. We first show results obtained in Europe where a moderate amplitude hydrological signal exists using both satellite (GRACE) and surface gravity measurements from the GGP (Global Geodynamics Project) network of superconducting gravimeters. We show also the nice agreement between ground and GRACE observations in Djougou (West Africa) where hydrological changes due to monsoon are important. We finally present on-going projects for the so-called 'null test' which is related to observations in a region with no (or very small) hydrological contribution to gravity. First results for the Sahara (Algeria) are reported and future missions in Egypt and Saudi Arabia briefly introduced.