Joint Research on the Chemistry of Stratospheric Ozone Loss

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Long-term decrease in the stratospheric ozone is prominent at mid-latitude around 45^o and is even larger at higher latitudes. The cause of this decrease is considered to be caused by the catalytic cycles by active chlorine species, which is produced through decomposition of CFCs. However, the observed decrease in ozone can not be explained by only gas phase chemistry. It is likely that heterogeneous processes occurring on the PSCs and sulfuric acid aerosols are playing important roles. However, direct observations of the heterogeneous processes in the atmosphere are still limited.We made balloon borne measurements of trace species from the CNES balloon launching center located at 44oN in France. Instruments to measure NO, HNO_3, NO_y, O_3, and aerosol were transported from Japan to France in January 1994. Instruments to measure stable chlorine species, N_2O, CH_4 and H_2O were prepared by the scientists of the Institute for Chemistry and Dynamics of the Geosphere. These instruments we … More re integrated into a gondola, which was launched in February and the profiles of these species from 10 to 32 km were measured. Aerosol concentration was found to be much higher than the background values below 20 km. After the balloon flight our NO, NO_y, and aerosol instruments were calibrated under low pressure and temperatures in Germany. These laboratory data are very important in the data reduction currently going on. Air samples collected on board the balloon were recovered successfully and are currently analyzed very precisely in Germany.During the period of the balloon experiment, we have made continuous measurements of stratospheric NO_2 and O_3 in Kiruna (68^oN) and Moshiri (44^oN). These data will be used in interpreting the balloon data.After the balloon experiment, NO and NO_y data obtained in the past were analyzed in conjunction with the tracer gases. A good liear relation between N_2O and NO_y in the lower stratosphere has been found. This relation will be useful for studies in the budget and partitioning of the reactive nitrogen. NO data are compared with lidar data obtained in Europe. Generally, NO values are lower when aerosols are enhanced due to volcanic eruptions, suggesting the effect of heterogeneous reaction on sulfuric acid aerosols. Less