Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 1 2003 10.5194/acpd-3-323-2003 http://www.atmos-chem-phys-discuss.net/3/323/2003/ http://www.atmos-chem-phys-discuss.net/3/323/2003/acpd-3-323-2003.html http://www.atmos-chem-phys-discuss.net/3/323/2003/acpd-3-323-2003.pdf 323 353 2003-01-29 A fast H₂O total column density product from GOME – validation with in-situ aircraft measurements T. Wagner J. Heland M. Zöger U. Platt Institut für Umweltphysik, University of Heidelberg, Germany 2Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany 3Deutsches Zentrum für Luft- und Raumfahrt (DLR), Flugabteilung, Oberpfaffenhofen, Germany Atmospheric water vapour is the most important greenhouse gas which is responsible for about 2/3 of the natural greenhouse effect, therefore changes in atmospheric water vapour in a changing climate (the water vapour feedback) is subject to intense debate. H₂O is also involved in many important reaction cycles of atmospheric chemistry, e.g. in the production of the OH radical. Thus, long time series of global H₂O data are highly required. Since 1995 the Global Ozone Monitoring Experiment (GOME) continuously observes atmospheric trace gases. In particular it has been demonstrated that GOME as a nadir looking UV/vis-instrument is sensitive to many tropospheric trace gases. Here we present a new, fast H₂O algorithm for the retrieval of vertical column densities from GOME measurements. In contrast to existing H₂O retrieval algorithms it does not depend on additional information like e.g. the climatic zone, aerosol content or ground albedo. It includes an internal cloud-, aerosol-, and albedo correction which is based on simultaneous observations of the oxygen dimer O₄. The high accuracy of our GOME H₂O data is confirmed by the excellent agreement with in-situ aircraft measurements during the MINOS campaign in Greece in summer 2001. Our H₂O algorithm can be directly adapted to the nadir observations of SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) which was launched on ENVISAT in March 2002. Near real time H₂O column data from GOME and SCIAMACHY might be of great value for meteorological weather forecast.