The global water cycle: where are the main challenges?

Jay Famiglietti
University of California, Irvine, USA

While the GRACE time-variable gravity mission has already made several important contributions to terrestrial and global hydrology, many key issues remain unresolved. In this presentation, several of these will be discussed, with implications for the design of a next-generation gravity mission. Examples for discussion include acceleration of the hydrological cycle, water mass changes in Earth’s land, ocean and ice reservoirs, land contributions to sea level rise, and future stresses on surface and groundwater availability. The need for higher space-time resolution information, and for user-friendly data products, will be highlighted, in order to increase the usage of satellite gravity information by the mainstream hydrologic community.