反演PM2.5(直径小于2.5 μm的颗粒物)质量浓度廓线，不仅可以估算污染物的柱浓度，还可研究污染物在空间的扩散规律，为防控大气环境污染提供科学支撑。假设在大气边界层内一次PM2.5质量浓度廓线的探测过程中，气溶胶的种类和成分保持不变，则根据地面上气溶胶消光系数与PM2.5质量浓度之间的比例关系，即可把激光雷达反演出的消光系数廓线转化为PM2.5质量浓度廓线。分析了两个晚上PM2.5质量浓度廓线个例及其随时空变化的情况，并对2014年3月至2015年2月探测到的82个晚上的数据按季节进行平均，获得了PM2.5质量浓度廓线的季节平均值。

Retrieving the profile of PM2.5 (particulate matter less than 2.5 μm in diameter) mass concentration can not only estimate column mass concentration of pollutants, but also follow pollutants diffusion rule in space, so as to provide scientific support for the prevention and control of atmospheric pollution. Suppose that the type and component of aerosol remain unchanged in the period of one PM2.5 mass concentration detection in the boundary layer, by using the proportional relation between the aerosol extinction coefficient and PM2.5 mass concentration at ground, the profile of PM2.5 mass concentration can be obtained from the profile of aerosol extinction coefficient which is retrieved by the lidar system. Two cases of PM2.5 mass concentration and the characteristic change with altitude and time are analyzed, and the 82 nights data measured from March 2014 to February 2105 are averaged by season. The average profile of seasonal PM2.5 mass concentration profile is calculated.