National Center for Atmospheric Research
Boulder, CO 80307, USA
The raw measurements of GPS radio occultation soundings are phase and amplitude of radio signals. It takes a number of steps to reduce the data to the traditional meteorological variables of temperature, pressure and water vapor. Because of the ray traversing geometry, the GPS radio occultation data have unique "pencil-like" measurement characteristics, which is very different from the point measurement of a radiosonde or an "area-average" measurement of a microwave sounder. To assimilate GPS radio occultation data effectively into a weather prediction model, one needs to correctly process the data and to properly account for the measurement characteristics and measurement errors. In this presentation, we will present the analysis of GPS radio occultation data from GPS/MET, CHAMP and SAC-C. We will discuss scientific and technical issues related to the assimilation of GPS radio occultation data into weather prediction models.