Near real‐time GPS sensing of atmospheric water vapor

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