TEMPORAL DEVELOPMENT OF MT-PINATUBO AEROSOLS AS OBSERVED BY LIDAR AND SUN PHOTOMETER AT NY-ALESUND, SPITSBERGEN

Since summer 1991 multiwavelength lidar and sun photometer observations of the Pinatubo aerosol layer are performed at the Arctic NDSC station (Koldewey-Station) in Ny-Alesund, Spitsbergen. The height integrated backscatter coefficient and the optical density decrease exponentially in time with time constants of 0.89+/-0.39 and 0.94+/-0.37 years, respectively. Their wavelength dependence indicates a decrease in median particle radii between 1992 and 1993. It is shown that the observations are consistent with results of parameter-free model calculations. The calculations are based on the assumption that gravitational sedimentation is the dominant process for volcanic aerosol removal in the Arctic stratosphere.