HR: 0800h
AN: U21C-0617    [Abstracts]
TI: Determination of dominant periodic components of water storage changes from GRACE and global hydrology models
AU: * Schmidt, R
EM: rschmidt@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Petrovic, S
EM: sp@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Guntner, A
EM: guentner@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Wunsch, J
EM: wuen@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Barthelmes, F
EM: bar@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Hengst, R
EM: rico@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Kusche, J
EM: jkusche@gfz-potsdam.de
AF: GeoForschungsZentrum (GFZ) Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AB: Variations of mass anomalies at the Earth's surface derived from monthly time series of global models of the Earth's gravity field of the US-German twin satellite mission GRACE (Gravity Recovery and Climate Experiment) clearly trace mass redistributions induced by continental hydrology. Previous studies indicate that such mass redistributions are dominated by annual and - in some regions - semiannual variations. In this contribution, we explicitly estimate for the first time the spectra of such dominant periodic patterns (in terms of periods, phases and amplitudes) that are not restricted to the fundamental annual frequency and its overtones. To this end we use a novel method that combines conventional empirical orthogonal functions (EOF) analysis with a determination of sine waves of arbitrary periods from the principal components based on time series of spatial maps of surface mass anomalies from GRACE and global hydrology models. The significance of the GRACE-derived spectra in view of the correlated GRACE data errors is assessed by means of a Monte-Carlo technique using available GRACE error covariance information. Considering only the significant, but dominating terms we can construct filtered GRACE data series which will serve for an improved validation and calibration of global hydrology models. This is demonstrated using the results from about 5 years of GRACE gravity fields of the GFZ-RL04 series and from independent state-of-the-art hydrology models. As one result our study reveals a systematic advance of the phases of the dominating annual terms of the hydrological models as compared to GRACE in the range of 1 to 6 weeks. This indicates deficiencies of the hydrological models w.r.t. runoff routing in the river network and/or water retention in lakes and wetlands. As a further result the analysis shows that besides annual and semiannual variations (specific only to some basins) also long-periodic signals with periods in the range of 2.1 to 2.5 years contribute to the periodic water storage variations. These may be related to long-term variations of the continental water storage (e.g. from the El Nino - Southern Oscillation) and comparisons to corresponding climatological indices will be presented.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1655 Water cycles (1836)
SC: Union [U]
MN: 2007 Fall Meeting