Chemistry of Stratospheric Ozone in the Arctic

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Total reactive nitrogen (NO_y), nitrous oxide (N_2O), and ozone (O_3) were measured on board a balloon launched from Aire sur 1' Adour (44ﾟN,0ﾟW), France on October 12,1994. Generally, NO _y was highly anti-correlated with N _2O and CH_4 at altitudes between 15 and 32 km. Slight departures from linear correlations occurred around 29 km, where N _2O and CH _4 mixing ratios were larger than typical midlatitude values, suggesting horizontal transport of tropical airmasses to northern midlatitudes in a confined altitude region.Simultaneous balloon-borne measurements of NO _y and N _2O were carried out from Kiruna (68ﾟN,21ﾟE) on February 11,1995. The minimum temperature at 465 K was near the type II PSCs formation thresholds from mid-December 1994 through mid-February 1995. NO_y mixing ratios which are expected from the NO _y-N_2O relationship obtained at mid-latitudes were derived. These values were compared with those observed. It has been found that the measured NO _y mixing ratios were much lower than those calculated around 19 km, suggesting strong denitrification.The NO/NO _y ratios observed on February 11,1995 is much higher than the values calculated from chemistry-trajectory models. We need to understand the cause of this discrepancy.A new Fourier Transform Spectrometer (FTS) was introduced for the observations in Kiruna. The instrument was tested in Germany in cooperation with the FZK group in January 1996. The FTS was transferred to Kiruna in March 1996 for long term observations of HCl, HF,HNO3, ClONO2, etc. Similar measurements have been made in northern Japan since July 1995. These data set will enable us to understand the chemical processes in the Arctic and midlatitudes.