German Title: Spektroskopische Messungen atmosphärischer Spurenstoffe auf der Neumayer-Station, Antarktis
Translation of abstract (English)
This thesis presents a two years record of Differential Optical Absorption Spectroscopy (DOAS) observations of zenith scattered sunlight at the German Antarctic research station Neumayer (70°S, 8°W). The measurements of the atmospheric trace gases ozone, NO2, OClO, BrO, IO and O4 were performed using a new UV/Vis spectrograph, developed within the scope of this work. The main intention of DOAS measurements in the Antarctic coastal region was to investigate the chemical composition of the stratosphere, particularly the influence of halogen compounds on the ozone layer, and to improve our understanding of the mechanisms leading to the ozone hole. The diurnal and seasonal variation of the observed stratospheric trace gases are in good agreement with the current understanding of atmospheric chemistry. Numerous strong and sudden enhancements of BrO were detected during August and September. These events were caused by BrO located in the lower troposphere, released by well known autocatalytic processes on acidified sea salt surfaces. Simultaneously, a strong depletion of near surface ozone was observed, caused by catalytic cycles involving bromine. A detailed analysis of the observed BrO events is presented, including surface ozone measurements, ozone soundings, the quantification of the radiative transport in the troposphere and a new approach to determine the source regions and the vertical distribution of reactive bromine. BrO was found to be transported from the sea ice surface to altitudes of more than 4000m. These processes possibly serve as an additional source for the recently speculated tropospheric BrO background. Within the scope of this work, the first detection of iodine oxide in the Antarctic marine boundary layer was possible. IO mixing ratios of approx. 5 - 10 ppt were estimated. In view of the fact that the ocean is the main source for reactive iodine in the troposphere, the constant IO levels observed throughout the year are a surprising finding.
|Date of thesis defense:||19 July 2001|
|Faculties / Institutes:||The Faculty of Physics and Astronomy > Institute of Environmental Physics|
|Controlled Keywords:||Atmosphäre / Chemie, Troposphäre, Stratosphäre, Antarktis, Ozonloch|