GPS RADIO OCCULTATION AT GFZ: STATUS AND RECENT RESULTS

The innovative GPS radio occultation (RO) remote sensing technique exploits atmospheric refraction and delay of GPS signals observed aboard Low Earth Orbiting (LEO) satellites. Observed phase path delays can be inverted to vertical profiles of bending angle, refractivity, temperature and humidity. Main properties of the calibration-free RO technique are insensitivity to clouds and rain, global coverage and high vertical resolution. The GPS RO technique is currently applied aboard several satellite missions (Metop, COSMIC, TerraSAR-X, GRACE-A, SAC-C). Since 2006, GPS RO data are operationally used in numerical weather prediction, significantly improving the forecast quality of the world-leading weather centres. On the other hand, the continuously growing GPS RO dataset (starting with the German geoscience satellite CHAMP in 2001) is of increasing interest for climatological investigations.

The operational GFZ orbit and occultation analysis system is currently in use for processing of GRACE-A and TerraSAR-X RO observations. Daily about 350 occultation events are analyzed and provided with average latency of less than 2 hours between measurement aboard the satellites and data provision via the GTS (Global Telecommunication Service) to the weather services (e.g., UK MetOffice, ECMWF, NCEP, DWD).

We overview the status of the operational RO analysis including validation with ECMWF analyses and radiosonde observations. We also present climatological applications regarding global temperature and tropopause trends and irregularities of the ionospheric E-region.