Stratospheric aerosol measurements by dual polarisation lidar

[摘要] 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 532nm laser andtwo polarisation channels in the receiver. When stratospheric aerosolamounts are very small, as at present, this method is, potentially, free ofa number of systematic errors that bedevil more commonly-used methods. Themethod rests on the assumption that the aerosol consists of sphericaldroplets which do not depolarise the lidar signal, which is valid under mostconditions. Maximum lidar ratios in background aerosol of 1.03-1.06 weremeasured during the period 2001-2004, with integrated backscatter in the range2-7x10^-5sr^-1. In January 2003, depolarising aerosol wasmeasured, which invalidated the dual-polarisation measurements. On 10-11 January,the depolarising aerosol was clearly a polar stratospheric cloud(the first lidar observations of such clouds in the British Isles) but theaerosol observed on 7-8 January was too low in altitude and too warm to be aPSC.

[学科分类] 大气科学