ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-153-2005 Subtropical trace gas profiles determined by ground-based FTIR spectroscopy at Izaña (28° N, 16° W): Five-year record, error analysis, and comparison with 3-D CTMs Schneider M. 1 Blumenstock T. 1 Chipperfield M. P. 2 Hase F. 1 Kouker W. 1 Reddmann T. 1 Ruhnke R. 1 Cuevas E. 3 Fischer H. 1 IMK-ASF, Forschungszentrum Karlsruhe, Karlsruhe, Germany Institute for Atmospheric Science, University of Leeds, Leeds, UK Observatorio Atmosférico de Izãna, Instituto Nacional de Meteorología, Spain 24 01 2005 5 1 153 167 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/5/153/2005/acp-5-153-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/153/2005/acp-5-153-2005.pdf

Within the framework of the NDSC (Network for the Detection of Stratospheric Change) ground-based FTIR solar absorption spectra have been routinely recorded at Iza&#241;a Observatory (28&deg; N, 16&deg; W) on Tenerife Island since March 1999. By analyzing the shape of the absorption lines, and their different temperature sensitivities, the vertical distribution of the absorbers can be retrieved. Unique time series of subtropical profiles of O<sub>3</sub>, HCl, HF, N<sub>2</sub>O, and CH<sub>4</sub> are presented. The effects of both dynamical and chemical annually varying trace gas cycles can be seen in the retrieved profiles. These include enhanced upwelling and photochemistry in summer and a more disturbed atmosphere in winter, which are typical of the subtropical stratosphere. A detailed error analysis has been performed for each profile. The output from two different three-dimensional (3-D) chemical transport models (CTMs), which are forced by ECMWF analyses, are compared to the measured profiles. Both models agree well with the measurements in tracking abrupt variations in the atmospheric structure, e.g. due to tropical streamers, in particular for the lower stratosphere. Simulated and measured profiles also reflect similar dynamical and chemical annual cycles. However, the differences between their mixing ratios clearly exceed the error bars estimated for the measured profiles. Possible reasons for this are discussed.