Intercomparison of ILAS-II version 1.4 and version 2 target parameters with MIPAS-Envisat measurements

摘要

This paper assesses the mean differences between the two ILAS-II dataversions (1.4 and 2) by comparing them with MIPAS measurements made betweenMay and October 2003. For comparison with ILAS-II results, MIPAS dataprocessed at the Institut für Meteorologie und Klimaforschung, Karlsruhe,Germany (IMK) in cooperation with the Instituto de Astrofísica deAndalucía (IAA) in Granada, Spain, were used. The coincidencecriteria of ±300 km in space and ±12 h in time for H₂O,N₂O, and CH₄ and the coincidence criteria of ±300 km in space and±6 h in time for ClONO₂, O₃, and HNO₃ were used. The ILAS-IIdata were separated into sunrise (= Northern Hemisphere) and sunset (=Southern Hemisphere). For the sunrise data, a clear improvement from version1.4 to version 2 was observed for H₂O, CH₄, ClONO₂, and O₃. Inparticular, the ILAS-II version 1.4 mixing ratios of H₂O and CH₄ wereunrealistically small, and those of ClONO₂ above altitudes of 30 kmunrealistically large. For N₂O and HNO₃, there were no largedifferences between the two versions. Contrary to the Northern Hemisphere,where some exceptional profiles deviated significantly from knownclimatology, no such outlying profiles were found in the Southern Hemispherefor both versions. Generally, the ILAS-II version 2 data were in betteragreement with the MIPAS data than the version 1.4, and are recommended forquantitative analysis in the stratosphere. For H₂O data in the Southern Hemisphere, further data quality evaluation is necessary.