Total reactive nitrogen, N2O, and ozone in the winter Arctic stratosphere

Total reactive nitrogen (NOy) and ozone were measured between 14 and 31 km during ascent on board a balloon launched from Kiruna, Sweden on January 31, 1992. Measurements of N2O were also made from the same gondola but during the fast parachute descent. Kiruna was located outside the polar vortex below 20 km and inside it above 23 km. The observed strong positive correlation between NOy and ozone as well as the negative correlation between NOy and N2O up to 22 km suggests the absence of denitrification at these altitudes. Very low N2O mixing ratios of about 13 ppbv were observed at altitudes between 23 and 27 km. In this region, the NOy mixing ratio was 13.6±0.5 ppbv, deviating from the above linear relationship by 6 ppbv. This deficit in NOy is interpreted in terms of downward transport of air from the upper stratosphere where photochemical NOy loss occurs.