Combination of NOAA16/ATOVS Brightness Tem- peratures and the CHAMP Data to get Temperature and Humidity Profiles

This paper examines whether the radio occultation (RO) measurements of the tropopause region are able to improve radiometric tropospheric profile retrievals, as represented by the ATOVS (Advanced TIROS Operational Vertical Sounder) temperature and humidity soundings from the NOAA16 (National Oceanic and Atmospheric Administration) satellite. First, a simulation study is presented wherein a statistical regression was used to infer temperature and humidity retrievals from ATOVS brightness temperatures and GPS (Global Positioning System) refractivity data. The ATOVS and GPS combination yields improved tropospheric profiles when compared to those inferred from either system alone. A sensitivity test was also performed to investigate how large GPS refractivity error can be and still improve the radiometric retrievals; even tripling the GPS refractivity observation errors yields improved retrievals. Second, the preparations to repeat the same study with real GPS (CHAMP) and ATOVS data are described. Collocations of GPS and CHAMP data were collected and the CHAMP data were evaluated against NWP profiles. CHAMP GPS validation suggested that CHAMP data would be able to improve the ATOVS retrievals as simulations with comparable GPS errors had showed positive retrieval impact. Future work will include application of regression approach for inferring retrievals after a statistically adequate number of collocations have been collected.