3. Gravity Changes over Russian River Basins from GRACE

Gravity Recovery and Climate Experiment (GRACE) twin satellites have been observing the mass transports of the Earth inferred by the monthly gravity field solutions in terms of spherical harmonic coefficients since 2002. In particular, GRACE temporal gravity field observations revolutionize the study of basin-scale hydrology, because gravity data reflect mass changes related to ground and surface water redistribution, ice melting, and precipitation accumulation over large scales. However, to use the GRACE data products, de-striping/filtering is required. We applied the multichannel singular spectrum analysis (MSSA) technique to filter GRACE data and separate its principal components (PCs) at different periodicities. Data averaging over the 15 largest river basins of Russia was performed. Spring 2013 can be characterized by the extremely large snow accumulation occurred in Russia. Melting of this snow induced large floods and abrupt increase of river levels. The exceptional maxima are evident from GRACE observations, which can be compared to the hydrological models, such as Global Land Data Assimilation System (GLDAS) or WaterGAP Global Hydrology Model (WGHM), and gauge data. Long-periodic climate-related changes were separated into PC 2. Finally, it was observed that there were mass increases in Siberia and decreases around the Caspian Sea. Overall trend over Russia demonstrates mass increase until 2009, when it had a maximum, followed by the decrease.