HR: 09:15h
AN: G31A-06    [Abstracts]
TI: Towards physical modeling of hydrological contribution in Strasbourg observatory
AU: * Longuevergne, L
EM: laurent.longuevergne@ccr.jussieu.fr
AF: UMR Sisyphe, 4 place Jussieu, Paris, 75252, France
AU: Boy, J
EM: boy@eost.u-strasbg.fr
AF: EOST, 5 rue Rene Descartes, Strasbourg, 67084, France
AU: Ferhat, G
EM: Gilbert.Ferhat@eost.u-strasbg.fr
AF: EOST, 5 rue Rene Descartes, Strasbourg, 67084, France
AU: Ulrich, P
EM: Patrice.Ulrich@eost.u-strasbg.fr
AF: EOST, 5 rue Rene Descartes, Strasbourg, 67084, France
AU: Florsch, N
EM: florsch@ccr.jussieu.fr
AF: UMR Sisyphe, 4 place Jussieu, Paris, 75252, France
AU: Hinderer, J
EM: jacques.hinderer@eost.u-strasbg.fr
AF: EOST, 5 rue Rene Descartes, Strasbourg, 67084, France
AB: Environmental forcings may influence geodetic measurements on a broad band of frequencies, ranging from long-term and annual variations to short-period disturbances of a few hours, possibly hiding internal processes. Hydrology, in particular, is pointed out to have a 100 nm.s-2 contribution. Two main difficulties arise: i) all environmental signals are correlated, especially on annual time scale and ii) gravimeters are sensitive to both local scale hydrology (water masses closer than 1km) and global scale hydrology (mass redistribution on the entire earth). As a consequence, fitting estimated corrections on geodetic data could lead to an incomplete correction of the environmental contribution and an incorrect evaluation of other environmental contributions (ocean especially). The hydrological contribution on gravimetric measurements is explored using physical modeling, and applied to the superconducting gravimeter in Strasbourg observatory. If global hydrological models may be used to model global scale contribution (e.g. LadWorld, GLDAS), local scale hydrology need a little more attention, both amount and position of water masses should be modelled. To this purpose, two multi-depth frequency-domain reflectometer (FDR) probes have been installed. They are monitoring the variation of the water content of the entire soil thickness with a 5-minute sampling since August 2005. A precise local DEM has been established using dGPS, the geometry and heterogeneity of the soil layer have been evaluated thanks to geophysical and geomecanical prospections. We show the great importance of the top soil layer in Strasbourg, since a one-meter thick soil may store an amount of 200 mm of a full layer of water (equivalent to a 80 nm.s-2 variation). This methodology also enable us to answer the question whether ground geodetic measurements may be used as tools for hydrologists.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1218 Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532)
DE: 1866 Soil moisture
DE: 1876 Water budgets
DE: 1895 Instruments and techniques: monitoring
SC: Geodesy [G]
MN: 2007 Fall Meeting