Das flugzeuggetragene Fernerkundungsexperiment MIPAS-FT: Auswertung und Interpretation der arktischen Meßkampagnen 1991/92 und 1992/93

The airborne remote sensing experiment MIP AS-FT: data analysis and interpretation of the arctic campaigns 1991/92 and 1992/93 This thesis deals with the data evaluation process and the interpretation of measurements performed in arctic and rnid-latitudes by the airborne Michelson-interferometer for Pa_ssivc Atmospheric SoundingFlugzeug Transall (MIPAS-FT) during the winter seasons 1991/92 and 1992/93. Sounding upward on a slant path through the atmosphere, the high-resolution spectrometer analyses the infrared radiation ernitted by the trace constituents. The aim of this work was to deduce colurnn amounts of trace gases from these measurements and to interpret their spatial structure and their temporal development with regard to their. importance to the chernistry of stratospheric ozone reduction. In the first part, the development of a strategy for the data analysis, starting with the raw data the interferograms and ending with the colurnn amounts of trace gases, is described. During that process many specific problems had to . be solved. In the beginning, the analysis consisted of quality-control and averaging of the interferograms. The effect of different interferences like clouds, errors in the digitalisation of the interferograms, electronic pulses, roll-angle rriovements or vibrations of the aircraft were exarnined. Some of these problems could be solved by singling out and correcting each interferogram. lt was shown that the effects of roll-angle movements, vibrations and periodic pulses are suppressed, similar to the spectral noise by averaging. Due to the background-ernission of the interferometer, it was not possible to use conventional methods of phase-correction of interferograms. Therefore, a new procedure for the deterrnination of the phase was employed and compared with other methods. Besides, an exarnination of the stability of the instrument showed that a correction of the blackbody-calibrated spectra was necessary. For that purpose, a correction method using C02-lines was developed. In order to derive colurnn amouri.ts of trace constituents all available external information about the present atmospheric conditions was used. Finally, the detailed procedure of the inversion process was deterrnined. In order to estimate the error of the calculated colurnn amounts, the contributions by many sources of error were evaluated. The main contributions are the radiometric calibration, the uncertainty of the temperature profile, and the assuptions made on the form of the height profile of the trace gases. In the second part of this work the colum amounts of the three stratospheric trace gases HN03, 0 3 and ClON02 deduced from the Transall-campaigns in the winter seaso~s 1991/92 and 1992/93 are presented and discussed. During the winter 1992/93 an interesting overall view of the chernical development of the polar vortex, from its conditioning phase until its disintegration, has been obtained. The chemical variation is most evidently reflected by the temporal development of ClON02 inside the vortex. This trace gas showed slightly enhanced values in December, very low column amounts in January, and an extreme increase in spring. During the cold period of the vortex a collar of ClON02, with higher values at the vortex edge, was observed. For the first time, a strong variability of the CION02 colurnn amounts at the vortex edge was noti-