Monitoring the vertical structure of the Arctic Polar Vortex over northern Scandinavia during EASOE: Regular N₂O profile observations

Different whole air samplers were flown on large balloons launched from Kiruna (67.9°N; 21.1°E) in the period from 30 November 1991 until 20 March 1992. Thirteen vertical profiles of the N₂O mixing ratio were obtained from the analyses of the stratospheric air samples collected at altitudes between about 10 km and 31 km. The series of profile observations illustrates the temporal variation of the vertical structure of the Arctic polar vortex over Northern Scandinavia during EASOE. Already by mid December the N₂O mixing ratios observed at the 600 K isentropic level (about 24–25 km) were as low as 20 ppbv, due to the effect of diabatic subsidence. In December subsidence rates of about 100–180 m/day were observed. Dynamic wave activity at the edge of the vortex led to significant sideways erosion at lower altitudes. However, inside the vortex, at altitudes above 600 K, N₂O mixing ratios of less than 10 ppbv were observed until the end of March.