Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 5 2006 10.5194/acpd-6-9765-2006 http://www.atmos-chem-phys-discuss.net/6/9765/2006/ http://www.atmos-chem-phys-discuss.net/6/9765/2006/acpd-6-9765-2006.html http://www.atmos-chem-phys-discuss.net/6/9765/2006/acpd-6-9765-2006.pdf 9765 9821 2006-10-05 Validation of MIPAS ClONO₂ measurements M. Höpfner T. von Clarmann H. Fischer B. Funke N. Glatthor U. Grabowski S. Kellmann M. Kiefer A. Linden M. Milz T. Steck G. P. Stiller P. Bernath C. E. Blom Th. Blumenstock C. Boone K. Chance M. T. Coffey F. Friedl-Vallon D. Griffith J. W. Hannigan F. Hase N. Jones K. W. Jucks C. Keim A. Kleinert W. Kouker G. Y. Liu E. Mahieu J. Mellqvist S. Mikuteit J. Notholt H. Oelhaf C. Piesch T. Reddmann R. Ruhnke M. Schneider A. Strandberg G. Toon K. A. Walker T. Warneke G. Wetzel S. Wood R. Zander Institut für Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, Germany Instituto de Astrofísica de Andalucía, Granada, Spain Department of Chemistry, University of Waterloo, Ontario, Canada Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division, Cambridge, MA, USA Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA Department of Chemistry, University of Wollongong, Australia Harvard-Smithsonian Center for Astrophysics, Optical and Infrared Astronomy Division, Cambridge, MA, USA Institut d’Astrophysique et de Géophysique, Université de Liège, Belgium Department of Radio and Space Science, Chalmers University of Technology, G¨oteborg, Sweden Institut für Umweltphysik, Universität Bremen, Germany Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA National Institute of Water and Atmospheric Research, Lauder, New-Zealand Altitude profiles of ClONO₂ retrieved with the IMK (Institut für Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izaña, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO₂. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30–35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11±0.12×10¹⁴ cm^−2 (1.0±1.1%) and −0.09±0.19×10¹⁴ cm^−2 (−0.8±1.7%), depending on the coincidence criterion applied. χ² tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS – FTIR or MIPAS – ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for χ² deviations. From the resulting χ² profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.