GPS ground networks for water cycle sensing

Tens of thousands of high-precision GPS receivers are operating around the world. With very few exceptions, the purpose of these receivers is to measure position. However, it is now known that GPS signals that reflect off nearby land surfaces and collected by these receivers can be used to measure shallow soil moisture variations, snow depth, and vegetation water content. These terrestrial water cycle products are distinctive in that they can be derived using widely-available GPS instruments. A water cycle portal created from data collected by a large GPS network in the western United States, the EarthScope Plate Boundary Observatory, is now available. It is updated daily at http://xenon.colorado.edu/portal. These data can be used for climate studies and satellite validation.