HR: 1340h
AN: G33B-0041    [Abstracts]
TI: Preliminary Tidal Analysis of GRACE Range-rate Data
AU: * Ray, R D
EM: richard.ray@nasa.gov
AF: NASA GSFC, Code 697, Greenbelt, MD 20771 United States
AU: Luthcke, S B
EM: sluthcke@bowie.gsfc.nasa.gov
AF: NASA GSFC, Code 697, Greenbelt, MD 20771 United States
AU: Rowlands, D D
EM: drowland@bowie.gsfc.nasa.gov
AF: NASA GSFC, Code 697, Greenbelt, MD 20771 United States
AB: GRACE range-rate residuals, calculated with respect to an initial gravity model and with appropriate corrections for non-conservative forces, can be transformed to in situ estimates of anomalous geopotential. After scaling and downward continuation, estimates of equivalent water level or other quantities of geophysical interest can be obtained. We use such a procedure to obtain simultaneous estimates of (1) the annual cycle, which is dominated by hydrological signals over continential regions, especially the Amazon, central and south-central Africa, and southeast Asia; and (2) the lunar tides M₂ and O_1. The lunar tidal estimates suggest that our prior model (GOT00) is in error in the Weddell and Ross Seas, in parts of the Arctic, especially the Canadian Archipelago, and in the Gulf of St Lawrence; these regions are expected to be in error because of lack of altimeter data or other difficulties. More surprisingly, the GRACE data also suggest possible errors in M₂ of a few cm in the Northeast Atlantic Ocean, which is an area of very large tidal range, but thought to be well constrained by altimetry. The solar tide signals in GRACE are problematic, because they are either coupled to the semiannual cycle or aliased to very long periods.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 4560 Surface waves and tides (1222)
SC: Geodesy [G]
MN: Fall Meeting 2005