COLUMN AMOUNTS OF CLONO2, HCL, HNO3, AND HF FROM GROUND-BASED FTIR MEASUREMENTS MADE NEAR KIRUNA, SWEDEN, IN LATE WINTER 1994

During SESAME phase I ground-based FTIR measurements were performed at Esrange near Kiruna, Sweden, from 28 January to 26 March 1994. Zenith column amounts of ClONO2, HCl, HF, HNO3, O-3, N2O, CH4, and CFC-12 we re derived from solar absorption spectra, Time series of ClONO2 and HC l indicate a chlorine activation at the end of January and around 1 Ma rch. On 1 March a very low amount of HCl of 2.09 x 10(15) molec. cm(-2 ) was detected, probably caused by a second chlorine activation phase starting from an already decreased amount of HCl. The ratio of column amounts of HCl to ClONO2 decreased inside the vortex from about 1 in J anuary to 0.4 in late March compared to values of about 2 outside the vortex. Although the Arctic stratosphere was rather warm in winter 199 3/94 and PSCs occurred seldom, chlorine partitioning into its reservoi r species HCl and ClONO2 changed during that winter and ClONO2 is the major chlorine reservoir at the end of the winter as in cold winters l ike 1991/92 and 1994/95.