Observations of Stratospheric NO 2 and O 3 at Thule, Greenland

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Abstract
Scattered sunlight and direct light from the moon was used in two wavelength ranges to measure the total column abundances of stratospheric ozone(O3) and nitrogen dioxide (NO2) at Thule, Greenland (76.5°N), during the period from 29 January to 16 February 1988. The observed O3 column varied between about 325 and 400 Dobson units, and the lower values were observed when the center of the Arctic polar vortex was closest to Thule. This gradient probably indicates that O3 levels decrease due to dynamical processes near the center of the Arctic vortex and should be considered in attempts to derive trends in O3 levels. The observed NO2 levels were also lowest in the center of the Arctic vortex and were sometimes as low as 5 x 1014 molecules per square centimeter, which is even less than comparable values measured during Antarctic spring, suggesting that significant heterogeneous photochemistry takes place during the Arctic winter as it does in the Antarctic.