| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2001 Stratospheric ozone is of crucial importance for life on Earth. This thin layer protects us from the ultraviolet solar radiation and also works as a greenhouse gas that helps maintaining our climate. Large changes in thickness and vertical distribution of the ozone abundance may have detrimental effects on life on Earth. But even small changes could have considerable impact on UV irradiance, bio-production and cancer rates. During the last decade record low spring time vertical column amounts of stratospheric ozone have been observed over Northern Europe. However, this decrease is not as severe as the depletion observed over Antarctica and at mid-latitudes in the Southern Hemisphere. The discovery of the spring time stratospheric ozone depletion first in Antarctica and later in the Arctic has triggered international research efforts on stratospheric ozone chemistry and the possible effects of human activities on the ozone layer. Ground-based differential optical absorption spectroscopy measurements of NO2 and ozone have been performed over Fairbanks (65�N) and Ny-Alesund (79�N) during the 1994--95 season. In this work we present improvements to ground based differential optical spectroscopy measurements by improving dark current corrections and spectral fitting of spectrographic photo diode array detector measurements. We have also improved the retrieval of vertical column amounts from diffuse light measurements by improving the corrections for seasonal changes in absorber air mass. This is particularly important at high latitudes. We used these data together with local weather and ozone sounding data, and with trace gas and aerosol data measured by other ground based instruments and by instruments deployed on satellites. This comprehensive dataset was used to investigate the performance of two current state of the art chemical transport models with and without the presence of heterogeneous chemistry. These are the University of Cambridge SLIMCAT model ...
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