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Polar stratospheric clouds play a key-role in polar ozone destruction. Cold temperatures in the vortex allow formation of these clouds. Depending on the PSC-type different formation-temperatures have to be reached. Synoptic temperatures do not always fall to these formation-temperatures, but waves in the atmosphere can lead to additional cooling of several 10 K, which allows PSC-formation. Whereas the wave-activity at the ESRANGE is very high due to hilly surrounding area, the orographic wave-activity at ALOMAR is expected to be rather small. Waves with long wavelengths will be present at both stations simultaneously. Coordinated measurements of temperature and aerosols will show both the large-scale wave-part and also the locally induced wave-part. Such measurements should allow identification of the different wavelngth scales and in addition contribute to a better estimate of the importance of wave-induced clouds for PSC-formation.
The purpose of the CHAOS_A project is to perform measurements under "Antarctic conditions" during the polar vortex period with the new assembled spectrometer in order to perform tasks that cannot be achieved at low latitudes namely OClO detection. Therefore the campaign focus more in technical aspects than scientific ones. The period of observation may be short to achieve results of scientific interest and those will depend on the meteorology of the stratosphere (position of the polar vortex relative to the station, temperatures at the lower stratosphere, etc). The OClO results will be compared with those obtained by the NILU (Andoya) and Heidelberg U.