Monitoring Continental Water Mass Variations by GRACE

Abstract:

The low-low satellite-to-satellite tracking mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, aims to determine Earth's static gravity field and its temporal variations. Geophysical mass changes at regional and global scale, which are related with terrestrial water bodies, ocean and atmosphere masses, melting and displacements of ice sheets and tectonic movements can be determined from time-dependent changes of the Earth's gravity field.

In this study, it is aimed to determine total water storage (TWS) (soil moisture, groundwater, snow and glaciers, lake and river waters, herbal waters) variations at different temporal and spatial resolution, monitoring the hydrologic effect causing time-dependent changes in the Earth's gravity field by two different methods. The region between 30°-40° northern latitudes and 36°-48° eastern longitudes has been selected as a study area covering the Euphrates - Tigris basin. TWS maps were produced with (i) monthly temporal and 400 km spatial resolution, based on monthly mean global spherical harmonic gravity field models of GRACE satellite mission (L2), and with (ii) monthly and semi-monthly temporal and spatial resolution as fine as 200 km based on GRACE in-situ observations (L1B).

Decreasing trend of water mass anomalies from the year 2003 to 2013 is proved by aforesaid approaches. Monthly TWS variations are calculated using two different methods for the same region and time period. Time series of both solutions are generated and compared.