Reasonably accurate satellite-based estimates of precipitation are the key to addressing many water-cycle based issues, from flood and drought monitoring and forecasting to sustainable water resources management to negotiationgs on transboundary basin agreements. The terretrial water cycle is driven by precipitation. However, many countries throughout the world suffer from a paucity of land-based weather stations, leading to challenges in the estimation of hydrologic stores and flows. G-WADI has supported the development of several such products - the PERSIANN family of products, from the University of California, Irvine, and MSWEP version 2.1, which is currently being led out of Princeton University.
The PERSIANN products are summarized here, and MSWEP 2.1 here.
The many precipitation products available have their strengths and weaknesses. For an exhaustive list of precipitation products (including products from satellite data, gauge data and combined sources) please visit the International Precipitation Working Group site at http://www.isac.cnr.it/~ipwg/data/datasets.html.