ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-3169-2008 Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS Müller S. C. 1 Kämpfer N. 1 Feist D. G. 2 Haefele A. 1 Milz M. 3 8 Sitnikov N. 4 Schiller C. 5 Kiemle C. 6 Urban J. 7 University of Bern, Bern, Switzerland Max-Planck-Institute for Biogeochemistry, Jena, Germany Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany Central Aerological Observatory, Moscow Region, Russia Forschungszentrum Jülich GmbH, Jülich, Germany DLR, Institut fuer Physik der Atmosphaere, Oberpfaffenhofen, Germany Chalmers University of Technology, Göteborg, Sweden now at: Luleå Technical University, Kiruna, Sweden 24 06 2008 8 12 3169 3183 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/3169/2008/acp-8-3169-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/3169/2008/acp-8-3169-2008.pdf

We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 0 to –20%, when compared to satellite experiments. Also a comparison between AMSOS and in-situ hygrosondes FISH and FLASH have been performed. A matching in the short overlap region in the upper troposphere of the lidar measurements from the DIAL instrument and the AMSOS dataset allowed water vapour profiling from the middle troposphere up to the mesosphere.

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