NEAR REAL-TIME GPS SENSING OF ATMOSPHERIC WATER-VAPOR

We describe sensing of atmospheric column water vapor in near real-tim e using the Global Positioning System (GPS). We use predicted GPS orbi ts for automated computation of vertical column water vapor within 30 minutes of GPS data collection. Based on a 4 month comparison, near re al-time GPS column water vapor agrees with radiosondes and radiometers within 2 mm rms. Our near real-time column water vapor data are poste d hourly at www.unavco.ucar.edu. They are available for assimilation i n numerical weather models and for other applications.