Global water cycle and climate change signals observed by satellite gravimetry

Terrestrial water storage (TWS) is an important parameter in water resource manages and research of land-surface processes and hydrological cycle. However, the traditional instruments are very difficult to monitor global high temporal-spatial terrestrial water storage and its variability without a comprehensive global monitoring network of hydrological parameters due to high cost and high labor intensity. The recent Gravity Recovery and Climate Experiment (GRACE) mission provides a unique opportunity to directly measure the global TWS and its change at multi-scales from August 2002 to February 2011. In this paper, the global terrestrial water storages with monthly resolution are derived from approximate 10 years of monthly GRACE measurements (2002 August-2011 February), and their changes at seasonal and long-term scales are investigated and compared with GLDAS (Global Land Data Assimilation System) model. Results show that significant annual variations of TWS are found at the globe, agreeing well with GLDAS model estimates. The secular trends are also observed at specific areas, reflecting extreme climate events, e.g., ice melting in Antarctica, Greenland, Canadian Islands, Alaska, Himalayan and Patagonia glaciers, La Plata drought in South American as well as floods in North Amazon, while the GLDAS model cannot capture these signals well.