Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 2 2005 10.5194/acpd-5-1529-2005 http://www.atmos-chem-phys-discuss.net/5/1529/2005/ http://www.atmos-chem-phys-discuss.net/5/1529/2005/acpd-5-1529-2005.html http://www.atmos-chem-phys-discuss.net/5/1529/2005/acpd-5-1529-2005.pdf 1529 1550 2005-03-15 Comparison of microwave satellite humidity data and radiosonde profiles: a survey of European stations V. O. John S. A. Buehler Institute of Environmental Physics, University of Bremen, Bremen, Germany A method to compare upper tropospheric humidity (UTH) from satellite and radiosonde data has been applied to the European radiosonde stations. The method uses microwave data as a benchmark for monitoring the performance of the stations. The present study utilizes three years (2002–2003) of data from channel 18 (183.31±1.00 GHz) of the Advanced Microwave Sounding Unit-B (AMSU-B) aboard the satellites NOAA-15 and NOAA-16. The comparison is done in the radiance space, the radiosonde data were transformed to the channel radiances using a radiative transfer model. The comparison results confirm that there is a dry bias in the UTH measured by the radiosondes. This bias is highly variable among the stations and the years. This variability is attributed mainly to the differences in the radiosonde humidity measurements. The results also hint at a systematic difference between the two satellites, the channel 18 brightness temperature of NOAA-15 is on average 1.0 K higher than that of NOAA-16. The difference of 1 K corresponds to approximately 7% relative error in UTH which is significant for climatological applications.