HR: 1340h
AN: G33A-0028    [Abstracts]
TI: Issues in the ground validation of satellite-derived gravity measurements; a proposal to validate GRACE in Africa from the Sahara to the equatorial monsoon zone
AU: * Hinderer, J
EM: Jacques.Hinderer@eost.u-strasbg.fr
AF: EOST/IPGS (UMR CNRS/ULP 7516), 5 rue Descartes, Strasbourg, 67084 France
AU: De Linage, C
EM: delinage@eost.u-strasbg.fr
AF: EOST/IPGS (UMR CNRS/ULP 7516), 5 rue Descartes, Strasbourg, 67084 France
AU: Boy, J
EM: jpboy@eost.u-strasbg.fr
AF: EOST/IPGS (UMR CNRS/ULP 7516), 5 rue Descartes, Strasbourg, 67084 France
AB: We will show in this paper the main difficulties arising in the ground validation of satellite-derived gravity observations. On one side, we will estimate the role played by the vertical motion of the measurement point located on the Earth's moving surface that alters gravity as measured by absolute or superconducting gravimeters on the contrary to the satellites. On the other side, we will pay attention to the length scales involved in hydrological processes which are different whether gravity is detected at the ground or by satellite. Examples using recent models of continental hydrology like LadWorld or GLDAS will be given. We will also present a proposal to validate GRACE observations with multi-disciplinary data (gravity, geodesy, hydrology, and meteorology) based on the detection of seasonal changes in water storage in Africa. We foresee to concentrate on two areas: the desert zone in the Sahara that provides a null test with almost no hydrological changes, and the equatorial monsoon band that provides a large rainfall signal. Our proposal will include two types of ground-based measurement campaigns. One is the repeated survey of 3 N-S absolute gravity profiles during two years to assess the large soil moisture changes as predicted by recent hydrological models. The second is to establish a high precision superconducting gravimeter (SG) at Nsimi (Cameroon) to act as a continuously monitored base station in a region of large soil moisture changes. In addition, we plan to include campaigns of continuous precise GPS measurements along the profiles to assess the vertical deformation not seen by the GRACE satellites. In-situ measurements of hydrological parameters at each station will assist us in modelling the local gravity effects at each station. Finally new approaches to generate highly tuned data (mascons) from GRACE satellites will be needed to maximize the time and spatial resolution of the satellite data in this area. The anticipated results of this project will strengthen the activities of the AMMA (Multi Disciplinary Model of African Monsoon) program. The ultimate goal is to combine all measurements to better characterize continental water storage, particularly in the critical areas of water management in the north and central portions of the African continent.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1866 Soil moisture
SC: Geodesy [G]
MN: Fall Meeting 2005