Global Climatologies Based on Radio Occultation Data: The CHAMPCLIM Project

The German/US research satellite CHAMP (CHAllenging Minisatellite Payload for geoscientific research) continuously records about 230 radio occultation (RO) profiles per day since March 2002. The mission is expected to last at least until 2007, thus CHAMP RO data provide the first opportunity to create RO based climatologies on a longer term. CHAMPCLIM is a joint project of the Wegener Center for Climate and Global Change (WegCenter) in Graz and the GeoForschungsZentrum (GFZ) in Potsdam. It aims at exploiting the CHAMP RO data in the best possible manner for climate research. For this purpose, CHAMP excess phase data provided by GFZ are processed at WegCenter with a new retrieval scheme, especially tuned for monitoring climate variability and change. The atmospheric profiles which pass all quality checks (∼150 profiles/day) are used to create climatologies on a monthly, seasonal, and annual basis. Here, we focus on dry temperature climatologies from the winter season (DJF) 2002/03 to the summer season (JJA) 2004, obtained by averaging-and-binning. The results show that useful dry temperature climatologies resolving horizontal scales >1000 km can be obtained even with data from a single RO receiver. RO based climatologies have the potential to improve modern operational climatologies, especially in regions where the data coverage and/or the vertical resolution and accuracy of RO data is superior to traditional data sources.