A Technical Note on Least Squares Mascon Fitting to GRACE Satellite Data to Estimate Total Water Storage Changes in the Middle East

Abstract

Nowadays the twin satellite gravimetry missions, GRACE (Gravity Recovery and Climate Experiment) and GRACE -Follow On, provide a unique and alternative tool for monitoring and measuring Total Water Storage (TWS) changes at different spatial and temporal scales, from regional, continental to global, and from intra-seasonal to long-term scales. TWS is a key parameter for hydrological studies such as monitoring of groundwater storage changes. This chapter focus on a detailed description of a technique named least squares mascon fitting which has been used for monitoring of TWS changes for specific regions of the Middle East such as Iran, Iraq, Syria, eastern Turkey, northern Saudi Arabia, southern Saudi Arabia, and the area immediately west of the Caspian Sea using GRACE data. This chapter is also dealing with results of our current research in Iran's water main basins. It shows that GRACE and GRACE FO data can be used to estimate TWS changes at a basin scale. The mascon analysis has less leakage error and can be used for hydrological applications without applying any gain factors or any post-processing in compare with other solutions such as the spherical harmonic solutions.