ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-7-2721-2007 Humidity observations in the Arctic troposphere over Ny-Ålesund, Svalbard based on 15 years of radiosonde data Treffeisen R. 1 Krejci R. 2 Ström J. 3 Engvall A. C. 2 Herber A. 4 Thomason L. 5 Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany Department of Meteorology (MISU), Stockholm University, S 106 91 Stockholm, Sweden ITM – Department of Applied Environmental Science, Stockholm University, S 106 91 Stockholm, Sweden Alfred Wegner Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany NASA Langley Research Center Hampton, VA 23681-2199, USA 24 05 2007 7 10 2721 2732 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/7/2721/2007/acp-7-2721-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/7/2721/2007/acp-7-2721-2007.pdf

Water vapour is an important component in the radiative balance of the polar atmosphere. We present a study covering fifteen years of data of tropospheric humidity profiles measured with standard radiosondes at Ny-Ålesund (78°55' N 11°52' E) during the period from 1991 to 2006. It is well-known that relative humidity measurements are less reliable at low temperatures when measured with standard radiosondes. The data was corrected for errors and used to determine key characteristic features of the vertical and temporal relative humidity evolution in the Arctic troposphere over Ny-Ålesund. We present frequencies of occurrence of ice-supersaturation layers in the troposphere, their vertical span, temperature and statistical distribution. Supersaturation with respect to ice shows a clear seasonal behaviour. In winter, (October–February) it occurred in 19% of all cases and less frequently in spring (March–May 12%), and summer (June–September, 9%). Finally, the results are compared with findings from the SAGE II satellite instrument on subvisible clouds.

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