Real-time national GPS networks: Opportunities for atmospheric sensing

Real-time national Global Positioning System (GPS) networks are being estab lished in a number of countries for atmospheric sensing. UCAR, in collabora tion with participating universities, is developing one of these networks i n the United States. The network, named "SuomiNet" to honor meteorological satellite pioneer Verner Suomi, is funded by the U.S. National Science Foun dation. SuomiNet will exploit the recently-shown ability of groundbased GPS receivers to make thousands of accurate upper and lower atmospheric measur ements per day. Phase delays induced in GPS signals by the ionosphere and n eutral atmosphere can be measured with high precision simultaneously along up to a dozen GPS ray paths in the field of view. These delays can be conve rted into total electron content (TEC), and integrated water vapor (if surf ace pressure data or estimates are available), along each GPS ray path. The resulting continuous, accurate, all-weather, real-time upper and lower atm ospheric data create a variety of opportunities for atmospheric research. I n this letter we describe SuomiNet, its applications, and the opportunity t o coordinate national real-time GPS networks to create a global network wit h larger scientific and operational potential.