Improved estimates of Antarctica seasonal and inter-annual ice mass variability from GRACE

Estimate of seasonal and inter-annual ice mass change in Antarctic from GRACE has been particularly difficult because of the large uncertainties in the estimates of Atmospheric mass correction from ECMWF model output. We compare geopotential heights from CHAMP GPS radio occultation (RO) and ECMWF model output to assess accuracy of the ECMWF estimates of atmospheric mass distribution. Because the CHAMP data are not assimilated into the ECMWF model this should provide an independent way to assess the accuracy of the ECMWF estimates. We analyze about 7 years of data between Jan 2002 to Sep 2008. We examine special and temporal differences between the two datasets, and we interpret those patterns in term of uncertainties in the two estimates of Atmospheric mass change. We compare those differences with GRACE derived mass changes over Antarctica and in light of this comparison we generate improved estimates of Antarctica seasonal and inter-annul ice surface mass balance from GRACE.