Validation of MIPAS-ENVISAT version 4.61 operational data: NO2

Abstract

Embedded in the ENVISAT validation programme of the chemistry instruments GOMOS, MIPAS, and SCIAMACHY a large number of balloon-borne, aircraft and ground-based measurements were successfully carried out in the years 2002 and 2003 in the Arctic and at mid-latitudes. Unfortunately, reanalyzed operational MIPAS data were only available for the year 2002 limiting the number of validation matches with the new version 4.61 data significantly. Apart from retrieval instabilities in the operational MIPAS profiles balloon-borne observations are in good agreement with the MIPAS satellite measurements. The same holds also for a satellite inter-comparison with HALOE (version 19) data. Compared to POAM III, MIPAS exhibits a low bias of about 20% in the middle and lower stratosphere. While aircraft measurements are not quantitatively rateable due to non-overlapping measurement altitudes, ground-based inter-comparisons show a high bias in the measured MIPAS partial columns compared to FTIR observations in Kiruna and, in contrary, a low bias compared to UV-vis measurements in Harestua. Further validation coincidences have to be considered before a final quantitative assessment on the quality of the MIPAS operational NO2 data is possible. Potential mismatches between two different sensors in terms of time and space need to be corrected with the help of photochemical model calculations taking into account the diurnal variation of the target species NO2.