我国西北半干旱区气溶胶类型的地基激光雷达判别

Aerosol types discrimination in semi-arid region of Northwest China using ground-based lidar data

气溶胶类型的准确识别是进一步研究其气候与环境效应的重要前提。基于兰州大学半干旱气候与环境观测站2009年10月至2012年11月地基双波长偏振激光雷达观测资料,分别在清洁天、人为污染物、沙尘事件和强沙尘暴事件4种典型情形下挑选若干个例,对其气溶胶消光系数、体积线性退偏比、气溶胶退偏比等进行统计分析,明确不同气溶胶类型的判定阈值。结果表明:清洁天该区域气溶胶消光系数小于0.085 km^(-1)。在消光系数大于该阈值的污染情形下,人为污染物的体积线性退偏比小于0.07,相应的气溶胶退偏比小于0.09;污染沙尘的体积线性退偏比介于0.07和0.22之间,气溶胶退偏比为0.09~0.31;纯沙尘的体积线性退偏比大于0.22,气溶胶退偏比大于0.31。当出现强沙尘暴时,体积线性退偏比大于0.35,气溶胶退偏比大于0.49。

The accurate identification of aerosol types is an important prerequisite for further research on its climatic and environmen⁃tal effects.In this study,based on the observation data of ground-based dual-wavelength polarization lidar from the Semi-arid Climate and Environment Observation Station of Lanzhou University from October 2009 to November 2012,several cases were selected under four typical scenarios:clean day,anthropogenic pollutants,dust events and strong sandstorm events.The aerosol extinction coefficient,volume linear depolarization ratio and aerosol depolarization ratio were analyzed statistically,and the determination thresholds of differ⁃ent aerosol types were defined.The results show that the extinction coefficient of aerosol in this region is less than 0.085 km^(-1) on clean day.When the extinction coefficient is greater than 0.085 km^(-1),the volume linear depolarization ratio of anthropogenic pollutants is less than 0.07,and the corresponding aerosol depolarization ratio is less than 0.09.The volume linear depolarization ratio of polluted dust is between 0.07 and 0.22,and the aerosol depolarization ratio is between 0.09 and 0.31.The volume linear depolarization ratio of pure dust is greater than 0.22,and the aerosol depolarization ratio is greater than 0.31.In particular,when severe sandstorms occur,the vol⁃ume linear depolarization ratio is greater than 0.35,and the aerosol depolarization ratio is greater than 0.49.