Ten-Day Gravity Field Solutions Inferred from GRACE Data

Abstract

The GRACE mission is designed to monitor temporal variations in the fluid mass at the surface of the Earth. 177 satellite-only geopotential solutions to degree and order 50 were computed every 10 days for the period 29 July 2002 through 30 September 2007. These solutions were obtained using a processing strategy, background model and solution stabilization in particular, which are different from the ones used by the GRACE project. A temporal and spatial resolution of 10 days and approximately 666 km (spherical harmonics up to degree 30) is achieved without significant streaking effects in the maps and good continuity across the solutions. The EIGEN-GL04C gravity field model, which is constructed exclusively with GRACE and LAGEOS data to degree and order 70, is used as the mean field to which all 10-day solutions are compared in order to infer temporal variations. After conversion to equivalent water height, the maps can be used to evaluate seasonal and linear variations in water mass storage. The uncertainty in the new solutions is estimated at 20–30 mm equivalent water height, or about 10% of the amplitude of the water mass variation of the Amazone basin.