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Abstract
Regular multi-wavelength Raman lidar observations of the vertical aerosol distribution have been performed at the Leibniz Institute for Tropospheric Research (IfT), Leipzig, Germany since 1996. From these measurements we obtain vertical profiles of backscatter coefficients at 355, 532, and 1064nm, extinction profiles at 355 and 532nm as well as depolarization ratio profiles at 532nm. From these optical data we derive microphysical parameters like effective radius and single-scattering albedo. IfT is an EARLINET station (European Aerosol Research LIdar NETwork) since 2000.
Our measurements in the past 12 years did not show any major event of aerosol pollution in the upper troposphere / lower stratosphere (UTLS). The situation changed after the strong eruptions of the Aleutian volcanoes Okmok and Kasatochi in July and August 2008. In the framework of our regular EARLINET observations we observe aerosol layers in the UTLS since August 2008. We observed maximum layer heights of about 19km in October 2008. Latest measurements in March 2009 show the main aerosol layer around the tropopause height, e.g., between 7 and 10km. We find traces of aerosols up to 14km.
We expect that the volcanic aerosols will be transported from the stratosphere into the troposphere by the tropopause faults in spring. Thus, in 2009 the stratosphere will be an additional source of aerosol particles in the free troposphere. We will document this development in spring and summer 2009 with our regular EARLINET observations. We will also present microphysical properties of the volcanic aerosols.