Validation of MIPAS ClONO2 measurementsReport as inadecuate

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1 IMK - Institute for Meteorology and Climate Research 2 IAA - Instituto de Astrofísica de Andalucía 3 Department of Chemistry 4 CfA - Harvard-Smithsonian Center for Astrophysics 5 Atmospheric Chemistry Division Boulder 6 Department of Chemistry 7 Institut d-Astrophysique et de Géophysique Liège 8 Department of Radio and Space Science Gothenburg 9 Institut für Umweltphysik 10 JPL - Jet Propulsion Laboratory 11 NIWA - National Institute of Water and Atmospheric Research Wellington

Abstract : 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. ?2 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 ?2 deviations. From the resulting ?2 profiles there is no evidence for a systematic over-underestimation of the MIPAS random error analysis.

Author: M. Höpfner - T. Von Clarmann - H. Fischer - B. Funke - N. Glatthor - U. Grabowski - S. Kellmann - M. Kiefer - A. Linden - M. Mil



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