Ozone and aerosol correlated observations at Thule, Greenland, in the period 1991-1994

Ozonesonde launches and ground-based lidar observations have been carried out at Thule, Greenland, during the winters 1991-1992, 1992-1993 and 1993-1994 following the Mt. Pinatubo eruption. The profiles thus obtained show large amounts of aerosols of volcanic origin in the lower stratosphere, and negatively correlated laminated structures in the ozone and in the aerosol content. The presence of these structures is confined to the region below approximately 18 km. The laminae are probably due to the spatial and temporal modulation induced by. the dynamics at the edge of the polar vortex: large differences exist in the aerosol and ozone concentration inside and outside the vortex. Averages of the correlation coefficient between the deviations of ozone and aerosol from their seasonal averages, calculated in 4-km height intervals for the quasi-simultaneous observations, are consistently negative in the 13- to 19-km region during the three winters. Minima of the average correlation coefficient occur at 18.5 km with -0.56 during 1991-1992, at 18 km (-0.69) during 1992-1993 and at 14.5 km (-0.38) during 1993-1994. Shortterm trajectory analysis do not provide firm evidence for chemical phenomena occurring on the surface of polar stratospheric clouds or volcanic aerosol: such possible actions appear to be masked by the dynamical phenomena.