Water Balance Estimates From Time-Variable Satellite Gravity

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0309678WahrMonthly solutions for the Earth's global gravity field,as provided bythe GRACE satellite mission, will be used to estimate and interpretmonth-to-month changes in the vertically-integrated distribution ofliquid water and snow stored on land.The spherical harmonic coefficients of the gravityfield provided by GRACE will beused to estimate mass variations averaged over continental regionson the Earth's surface.This will involve the construction ofaveraging functions that are specially tailoredfor those regions.These variations will be interpreted interms of changes in the mass of water stored in those regions.Among the things that will be estimated and interpreted are:changes in the total amount of water stored within large regions (greaterthan 200,000 square km);precipitation minus evaporation averagedover large river basins;changes in snowpack at northern latitudes; andchanges in the total water stored in regions withlarge underground aquifers.This work, which will form the PhD thesisproject of a graduate student,will be a first step towards integrating time-variablesatellite gravity observations into the hydrological sciences.These observations constitute a new and innovative data type for hydrology,with considerable promise for improved understandingof the global water cycle.