HR: 1340h
AN: G43B-1211    [Abstracts]
TI: GHYRAF (Gravity and HYdrology in AFrica): an Experiment to Validate GRACE in Africa From the Sahara to the Equatorial Monsoon Zone
AU: * Hinderer, J
EM: Jacques.Hinderer@eost.u-strasbg.fr
AF: IPG Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, Strasbourg, 67084, France
AU: de Linage, C
EM: delinage@eost.u-strasbg.fr
AF: IPG Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, Strasbourg, 67084, France
AU: Boy, J
EM: jpboy@eost.u-strasbg.fr
AF: IPG Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, Strasbourg, 67084, France
AU: Gegout, P
EM: pgegout@eost.u-strasbg.fr
AF: IPG Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, Strasbourg, 67084, France
AU: Masson, F
EM: frederic.masson@eost.u-strasbg.fr
AF: IPG Strasbourg (UMR 7516 CNRS-ULP), 5 rue Descartes, Strasbourg, 67084, France
AU: Diament, M
EM: diament@ipgp.jussieur.fr
AF: Geosciences Montpellier, 4 place Bataillon, Montpellier, 34095, France
AU: de Viron, O
EM: deviron@ipgp.jussieu.fr
AF: Geosciences Montpellier, 4 place Bataillon, Montpellier, 34095, France
AU: Bayer, R
EM: Roger.Bayer@gm.univ-montp2.fr
AF: IPG Paris, 4 place Jussieu, Paris, 75252, France
AU: Balmino, G
EM: balmino@dtp.obs-mip.fr
AF: DTP, OMP 14 av. Belin, Toulouse, 31400, France
AU: Biancale, R
EM: biancale@dtp.obs-mip.fr
AF: DTP, OMP 14 av. Belin, Toulouse, 31400, France
AU: Bonvalot, S
EM: bonvalot@lmtg.obs-mip.fr
AF: LMTG, OMP 14 av. Belin, Toulouse, 31400, France
AU: Genthon, P
EM: genthon@msem.univ-montp2.fr
AF: Hydrosciences Montpellier, Maison des Sciences de l'eau place Bataillon, Montpellier, 34095, France
AB: We present an experiment to validate GRACE observations with multi-disciplinary data (gravity, geodesy, hydrology, and meteorology) based on the observation 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 on the contrary a large rainfall signal. Our proposal includes two types of ground-based gravity measurements. First we will perform a repeated survey with absolute gravimeters (AG) on a North-South profile during a 2-3 year time span (2008-2010) to assess the large soil moisture changes as predicted by existing hydrological models. Second we plan to establish a superconducting gravimeter (SG) to act as a continuously monitored base station in a region of large soil moisture changes. In addition, continuous geodetic GPS measurements will be made along the profile to assess the vertical deformation which is not seen by GRACE. In-situ measurements of hydrological parameters at each station will assist us in modelling local gravity effects. We will point out 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 AG or SG on the contrary to satellites. On the other side, we will pay attention to the length scales involved in hydrological processes which are differently retrieved whether gravity is measured at the ground or by satellite. Examples using recent models of continental hydrology such as LadWorld or GLDAS will be given.
DE: 1200 GEODESY AND GRAVITY
DE: 1217 Time variable gravity (7223, 7230)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1800 HYDROLOGY
DE: 1876 Water budgets
SC: Geodesy [G]
MN: 2007 Fall Meeting