Analysis Of Tropospheric Aerosol Data In The Northern Suburbs Of Nanjing Based On Raman-Mie Lidar

In this paper,the optical properties of tropospheric aerosols in the northern suburbs of Nanjing are analyzed using Rayleigh-Raman-meter lidar data from the observation site of Nanjing University of Information Science and Technology.When using Fernald method to solve Mie scattering echo signal,we analyze the selection of parameters.Firstly,the selection of methods for removing background noise of signals is analyzed.It is found that it is reasonable to treat the average echo of clean atmosphere 10 km away as background noise.Taking Fernald inversion method as an example,the influence of boundary value and lidar ratio on inversion results is analyzed.When the boundary value is about 8×10^-3km^-1,the difference of aerosol extinction coefficient obtained by inversion will not be very large.When the aerosol concentration is large,the extinction coefficient obtained by inversion increases with the increase of the selected boundary value,when the aerosol concentration is small,the impact can be neglected.When the value of lidar ratio varies between 20 and 70,the change of lidar ratio has little effect on the aerosol extinction coefficient obtained by inversion.When using the Raman channel echo signal to solve the aerosol extinction coefficient,the selection of various parameters of wavelet denoising method is studied.First analyze the four different adaptive thresholds,then discuss the selection of soft and hard threshold functions.The adaptive threshold chooses the fixed form of`sqtwolog',and the soft threshold is chosen to reduce the threshold.This method has better denoising effect for Raman channel echo signal and smoother aerosol extinction coefficient profile retrieved.The echo data of the Mie channel is used to analyze the examples observed by the lidar,the correlation law of aerosols in the region and the analysis of a smog pollution process.The echo signal of the Raman channel is used to invert the aerosol extinction coefficient of the troposphere,and the tropospheric high aerosol backscatter coefficient and the lidar ratio are combined with the signal of the Mie channel.The results show:?1?Through the analysis of data inversion results of Lidar Mie channel,it can be seen that lidar can detect the changes of clouds and clouds in a period of time in time because of its high temporal resolution,and can also roughly judge the information of cloud height according to the change of echo signal strength.?2?Rayleigh-Raman-Mie laser radar can directly invert the aerosol extinction coefficient,backscattering coefficient and lidar ratio without assuming the laser radar ratio,and can roughly identify the aerosol species.The area of the cirrus has a Lidar ratio of 17±10 sr.?3?Human production and life in the northern suburbs of Nanjing have a certain impact on the distribution of high aerosols.In the cloudless region between 4 and 8.7 km,the extinction coefficient of aerosol ranges from 0.03 to 0.07 km^-1,the backscattering coefficient ranges from 0.011 to 0.024 km^-1sr^-1,the range of lidar ratio is 22-52s,they are all higher than the atmospheric model,indicating that there is a certain amount of aerosol in the northern suburbs of Nanjing.