"SuomiNet, " a university—based, real—time, national Global Positioning System (GPS) network, is being developed for atmospheric research and education with funding from the National Science Foundation and with cost share from collaborating universities. The network, named to honor meteorological satellite pioneer Verner Suomi, will exploit the recently shown ability of ground—based GPS receivers to make thousands of accurate upper— and lower—atmospheric measurements per day. Phase delays induced in GPS signals by the ionosphere and neutral atmosphere can be measured with high precision simultaneously along a dozen or so GPS ray paths in the field of view. These delays canbe converted into integrated water vapor (if surface pressure data or estimates are available) and total electron content(TEC), along each GPS ray path. The resulting continuous, accurate, all—weather, real—time GPS moisture data will helpadvance university research in mesoscale modeling and data assimilation, severe weather, precipitation, cloud dynamics, regional climate, and hydrology. Similarly, continuous, accurate, all—weather, real—time TEC data have applications in modeling and prediction of severe terrestrial and space weather, detection and forecasting of low—altitude ionospheric scintillation activity and geomagnetic storm effects at ionospheric midlatitudes, and detection of ionospheric effects induced by a variety of geophysical events. SuomiNet data also have potential applications in coastal meteorology, providing ground truth for satellite radiometry, and detection of scintillation associated with atmospheric turbulence inthe lower troposphere. The goal of SuomiNet is to make large amounts of spatially and temporally dense GPS—sensed atmospheric data widely available in real time, for academic research and education. Information on participation in SuomiNet is available via www.unidata.ucar.edu/suominet.