Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 1 2004 10.5194/acpd-4-299-2004 http://www.atmos-chem-phys-discuss.net/4/299/2004/ http://www.atmos-chem-phys-discuss.net/4/299/2004/acpd-4-299-2004.html http://www.atmos-chem-phys-discuss.net/4/299/2004/acpd-4-299-2004.pdf 299 325 2004-01-16 Ice supersaturation as seen from TOVS K. Gierens klaus.gierens@dlr.de R. Kohlhepp P. Spichtinger M. Schroedter-Homscheidt Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany Deutsches Zentrum für Luft- und Raumfahrt, Deutsches Fernerkundungsdatenzentrum, Oberpfaffenhofen, Germany We have analysed the upper tropospheric humidity with respect to ice (UTHi) data product obtained from the Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) instrument onboard the National Oceanic and Atmospheric Administration NOAA-14 polar orbiting satellite. While in the production of the official UTHi product values in excess of 100% are ignored, we do not so – in view of many recent results obtained from a variety of other in-situ and remote sensing instruments showing that ice supersaturation frequently occurs in the upper troposphere. We show that TOVS is able to detect ice supersaturation at the correct locations (however, only in less than one percent of its soundings, presumably because of TOVS's low vertical resolution), and that the supersaturation follows the well known exponential behaviour. We conclude that values of UTHi in excess of saturation should not be considered a measurement error anymore. The similar re-analysis of TOVS data back to 1979 could give important insights into trends of upper tropospheric humidity.