Stratospheric aerosol measurements by dual polarisation lidar

Abstract

We present measurements of stratospheric aerosol made at Aberystwyth, UK (52.4°N, 4.06°W) during periods of background aerosol conditions. The measurements were made with a lidar system based on a 532 nm laser and two polarisation channels in the receiver. When stratospheric aerosol amounts are very small, as at present, this method is, potentially, free of a number of systematic errors that bedevil more commonly-used methods. The method rests on the assumption that the aerosol consists of spherical droplets which do not depolarise the lidar signal. We show that this assumption, while sometimes valid, cannot always be assumed so.