Impact of aerosol hygroscopic growth on retrieving aerosol extinction coefficient profiles from elastic-backscatter lidar signals

摘要

Light detection and ranging (lidar) measurements have been widelyused to profile the ambient aerosol extinction coefficient(). The particle extinction-to-backscatterratio (lidar ratio, LR), which strongly depends on the aerosol dryparticle number size distribution (PNSD) and aerosol hygroscopicity,is introduced to retrieve the profile fromelastic-backscatter lidar signals. Conventionally, a constantcolumn-integrated LR that is estimated from aerosol optical depth isused by the retrieving algorithms. In this paper, the influences ofaerosol PNSD, aerosol hygroscopic growth and relative humidity (RH)profiles on the variation in LR are investigated based on thedatasets from field measurements in the North China Plain(NCP). Results show that LR has an enhancement factor of 2.2 when RHreaches 92 %. Simulation results indicate that both themagnitude and vertical structures of the profiles by using the column-related LR method are significantly biasedfrom the original profile. The relative bias,which is mainly influenced by RH and PNSD, can reach up to 40 %when RH at the top of the mixed layer is above 90 %. A newalgorithm for retrieving profiles and a newscheme of LR enhancement factor by RH in the NCP are proposed inthis study. The relative bias between the profile retrieved with this new algorithm and the ideal true valueis reduced to below 13 %.