米-拉曼散射激光雷达反演对流层气溶胶消光系数廓线

Inversion of Tropospheric Aerosol Extinction Coefficient Profile by Mie-Raman Scattering Lidar

介绍了基于米-拉曼散射激光雷达的南京北郊大气气溶胶观测实验,采用小波分析中的软硬阈值方式处理拉曼散射激光雷达回波信号,选取不同的阈值和不同的小波函数处理拉曼散射激光雷达回波信号,得到了平滑的拉曼散射激光雷达信号。根据拉曼散射激光雷达原理反演对流层高空大气气溶胶消光系数廓线,借助弗纳尔德方法并利用米散射激光雷达气溶胶观测数据,反演得到对流层低空大气气溶胶消光系数廓线。实验观测系统中有瑞利、米散射和拉曼散射3个接收通道,重点研究了米散射和拉曼散射通道接收到的观测数据,对南京北郊2011-12-08晚间拉曼散射激光雷达的气溶胶观测数据进行4种不同阈值处理。选择合适的阈值对实验观测数据进行去噪,然后利用反演原理公式并结合距离矫正信号对观测数据进行反演,得到对流层高空大气气溶胶消光系数廓线;利用其中一处的气溶胶消光系数可以反演得到对流层低空大气气溶胶消光系数廓线。利用米-拉曼散射激光雷达联合反演对流层气溶胶消光系数廓线,可以清晰看出气溶胶的分布特征,对流层低空自由大气的气溶胶消光系数最大值一般为0.1km^(-1)左右,表明对流层低空自由大气比较干净;对流层高空大气气溶胶消光系数在云影响下可达到6km^(-1),无云时气溶胶消光系数最大值一般为0.1km^(-1)左右,表明高空大气比较干净。

An observation experiment of atmospheric aerosol based on Mie-Raman scattering lidar in northern suburb of Nanjing is introduced. A soft and hard threshold method is used to deal with Raman scattering lidar＇s echo signal with wavelet analysis, and different thresholds and different wavelet functions are selected to process the Raman scattering lidar＇s echo signal. Smoothed Raman scattering lidar＇s echo signal is obtained. Upper tropospheric atmospheric aerosol extinction coefficient profiles are inversed based on Raman scattering lidar principle. With the Fernald method and the Mie scattering lidar＇s observation data of aerosol, the atmospheric aerosol extinction coefficient profile in low tropospheric can be obtained. There are three receiving channels in the experimental observation system, including Rayleigh, Mie and Raman scattering channels. The data observed in Mie and Raman scattering channels are mainly studied. Raman scattering lidar＇s aerosol observational data on 2011-12-08 in northern suburb of Nanjing is processed by four different thresholds. Appropriate threshold is selected to denoise the experimental observed data, and we use the formula of the inversion principle and combine with the distance correction signal to inverse the observed data, and the extinction coefficient profiles of the upper tropospheric atmospheric aerosol are obtained, The aerosol extinction coefficient profiles of low troposphere atmospheric aerosol can be retrieved based on one of the aerosol extinction coefficients of upper tropospheric atmospheric aerosol. After the Mie-Raman scattering lidar joint inversion of tropospheric aerosol extinction coefficient profile, we can clearly find the distributions of aerosol characteristics. The maximum value of aerosol extinction coefficient of low tropospheric free atmosphere is generally about 0.1 km-1 , and it shows that free atmospheric of low tropospheric is relatively clean. The aerosol extinction coefficient of upper tropospheric can reach 6 km-1 under the influence of the cloud, and the maximum value of aerosol extinction coefficient is about 0.1 km-1 when there is no cloud. The result shows that the upper atmosphere is relatively clean.