BACKSCATTER MEASUREMENTS OF STRATOSPHERIC AEROSOLS AT THULE DURING JANUARY-FEBRUARY 1992

Within the European Arctic Stratospheric Ozone Experiment (EASOE) aero sols from the volcanic eruption of Mt. Pinatubo have been observed dur ing 6 balloonborne backscatter soundings in January and February 1992 under different polar vortex conditions from Thule, Greenland. The vor tex boundary seemed to retard stratospheric aerosol mixing into the in ner parts of the vortex from lower latitudes; however, when Thule was outside the vortex large aerosol loadings were measured. The aerosols were simultaneously observed by groundbased lidar, whereby aerosol bac kscatter measurements in three different wavelengths made it possible to obtain information about the particle sizes. Parameters of lognorma l distributions have been derived, using a least square approach betwe en observed and calculated backscatter coefficients from Mie theory. T he aerosol surface area density was increased by factors 10-50, compar ed to the background levels at pre-volcanic conditions.