Measurements of NO2 and HNO3 during a stratospheric warming at 54°N in February 1979

The altitude distribution of HNO3 was measured during a stratospheric warming on a balloon flight from Cold Lake, Alberta, on 11 February, 1979. The HNO3 profile measured appears to be layered and have a greater thickness than that of a typical summer profile. Ground based observations of the zenith sky were made from 31 January to 12 February and yield the total abundance of stratospheric NO2. Stratospheric NO2 column amounts deduced from these ground based measurements and another set taken during February, 1977 exhibit a diurnal variation under dynamical conditions of both stable vortex flow (1977) and stratospheric warming (1979). Using these measurements, the NO measurements of Knight et al. (1982), and model calculations we find that above 20 km there does not appear to be a pronounced seasonal change in total odd nitrogen. However, below 24 km the conversion of NOw = NO + NO2 + 2 × N2O5 + HO2NO2 to HNO3 occurs more rapidly than calculated using current homogeneous chemistry.