Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 2 2007 10.5194/acpd-7-5173-2007 http://www.atmos-chem-phys-discuss.net/7/5173/2007/ http://www.atmos-chem-phys-discuss.net/7/5173/2007/acpd-7-5173-2007.html http://www.atmos-chem-phys-discuss.net/7/5173/2007/acpd-7-5173-2007.pdf 5173 5251 2007-04-17 Validation of MIPAS HNO₃ operational data D. Y. Wang M. Höpfner C. E. Blom W. E. Ward H. Fischer T. Blumenstock F. Hase C. Keim G. Y. Liu S. Mikuteit H. Oelhaf G. Wetzel U. Cortesi F. Mencaraglia G. Bianchini G. Redaelli M. Pirre V. Catoire N. Huret C. Vigouroux M. De Mazière E. Mahieu P. Demoulin S. Wood D. Smale N. Jones H. Nakajima T. Sugita J. Urban D. Murtagh C. D. Boone P. F. Bernath K. A. Walker J. Kuttippurath A. Kleinböhl G. Toon C. Piccolo Forschungszentrum Karlsruhe und Universität Karlsruhe, Institut für Meteorologie und Klimaforschung (IMK), Karlsruhe, Germany Physics Department, University of New Brunswick, Fredericton, New Brunswick, Canada Istituto di Fisica Applicata "N. Carrara" (IFAC) del Consiglio Nazionale delle Ricerche (CNR), Firenze, Italy CETEMPS, Universita' di L'Aquila, Dipartimento di Fisica, L'Aquila, Italy Laboratoire de Physique et Chimie de l'Environnement, Université d'Orléans (LPCE-CNRS), Orléans, France Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium Institut d'Astrophysique et de Géophysique, University of Liège (ULg), Liège, Belgium National Institute for Water and Atmospheric Research (NIWA), Lauder, Otago, New Zeland University of Wollongong, Wollongong, Australia National Institute for Environmental Studies, Tsukuba, Japan Chalmers University of Technology, Department of Radio and Space Science, Göteborg, Sweden Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada Department of Chemistry, University of York, Heslington, York, UK Department of Physics, University of Toronto, Toronto, Canada Institute of Environmental Physics, University of Bremen, Bremen, Germany CNRS/LMD Ecole Polytechnique, Palaiseau Cedex, France Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA Department of Physics, Oxford University, Oxford, UK Nitric acid (HNO₃) is one of the key products that are operationally retrieved by the European Space Agency (ESA) from the emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. The product version 4.61/4.62 for the observation period between July 2002 and March 2004 is validated by comparisons with a number of independent observations from ground-based stations, aircraft/balloon campaigns, and satellites. Individual HNO₃ profiles of the ESA MIPAS level-2 product show good agreement with those of MIPAS-B and MIPAS-STR (the balloon and aircraft version of MIPAS, respectively), and the balloon-borne infrared spectrometers MkIV and SPIRALE, mostly matching the reference data within the combined instrument error bars. In most cases differences between the correlative measurement pairs are less than 1 ppbv (5–10%) throughout the entire altitude range up to about 38 km (~6 hPa), and below 0.5 ppbv (15–20% or more) above 30 km (~17 hPa). However, differences up to 4 ppbv compared to MkIV have been found at high latitudes in December 2002 in the presence of polar stratospheric clouds. The degree of consistency is further largely affected by the temporal and spatial coincidence, and differences of 2 ppbv may be observed between 22 and 26 km (~50 and 30 hPa) at high latitudes near the vortex boundary, due to large horizontal inhomogeneity of HNO₃. Similar features are also observed in the mean differences of the MIPAS ESA HNO₃ VMRs with respect to the ground-based FTIR measurements at five stations, aircraft-based SAFIRE-A and ASUR, and the balloon campaign IBEX. The mean relative differences between the MIPAS and FTIR HNO₃ partial columns are within ±2%, comparable to the MIPAS systematic error of ~2%. %This should be the systematic error without spectroscopy since the ground-based data were retrieved using the same version of the HITRAN database. For the vertical profiles, the biases between the MIPAS and FTIR data are generally below 10% in the altitudes of 10 to 30 km. The MIPAS and SAFIRE \chem{HNO_3} data generally match within their total error bars for the mid and high latitude flights, despite the larger atmospheric inhomogeneities that characterize the measurement scenario at higher latitudes. The MIPAS and ASUR comparison reveals generally good agreements better than 10–13% at 20–34 km. The MIPAS and IBEX measurements agree reasonably well (mean relative differences within ±15%) between 17 and 32 km. Statistical comparisons of the MIPAS profiles correlated with those of Odin/SMR, ILAS-II, and ACE-FTS generally show good consistency. The mean differences averaged over individual latitude bands or all bands are within the combined instrument errors, and generally within 1, 0.5, and 0.3 ppbv between 10 and 40 km (~260 and 4.5 hPa) for Odin/SMR, ILAS-II, and ACE-FTS, respectively. The standard deviations of the differences are between 1 to 2 ppbv. 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