SOME RESULTS OF WATER-VAPOR, OZONE AND AEROSOL BALLOON-BORNE MEASUREMENTS DURING EASOE

As part of the European Arctic Stratospheric Ozone Experiment (EASOE) in the northern winter of 1991/92, regular measurements of the vertica l distribution of ozone and aerosols were carried out from two Russian polar stations, Heiss Island (81N,58E) and Dikson Island (73N,81E). I n addition measurements of the vertical distribution of water vapor an d aerosols were made from Esrange (68N,21E), near Kiruna in Sweden. Th e instruments used were electrochemical ozone sondes (ECC-4A), a fluor escence hygrometer, and the University of Wyoming backscattersonde. Fo llowing the eruption of Mt.Pinatubo, in the Philippines, in June 1991, volcanic aerosol had reached Arctic latitudes at altitudes below 19 k m by September. At all three sites it was observed on every flight. Po lar stratospheric clouds were encountered above the volcanic aerosol o n two flights from Esrange. There were no indications of dehydration i n the Arctic stratosphere. On all flights the minimum mixing ratio of water vapor was observed 2 to 3 km above the tropopause. Total ozone w as much lower than the climatological mean, over Dikson Island from th e January 27, and over Heiss Island from mid-February, until the end o f EASOE. Ozone profiles over these stations showed rapid increases in partial pressure immediately above the peak values of backscatter rati o when the volcanic aerosol was especially dense.