Lidar Detecting The Diel Variations Of Atmospheric Aerosol Optical Depth In Hefei Area

In order to enrich the measuring methods of the entire atmospheric aerosol optical depth,a method of integrating micro-pulse lidar and surface visibility data to detect the entire atmospheric aerosol optical depth is proposed.Firstly,the atmospheric aerosol is introduced from the basic properties,classification,spectral distribution,aerosol effect and its optical characteristics.Several common aerosol detection methods are briefly described.Among them,the sun photometer has good accuracy,but it is limited to the measurement of the day.The advantages of using lidar to continuously measure the relevant characteristics of atmospheric aerosols have been carried out throughout the year for a continuous year.Taking January and July as an example,preprocess the echo signal obtained by lidar,use Fernald algorithm to invert the extinction coefficient in the vertical direction,filter the effective data to calculate the aerosol scale height,according to Koschmieder's law,use visibility data to find the surface extinction coefficient,and finally obtain the entire layer of atmospheric aerosol optical depth,discussed the day and night distribution characteristics and influencing factors.It provides a new idea for calculating the entire atmospheric aerosol optical depth at night.Specific steps are as follows:1.The Fernald method is used to retrieve the aerosol vertical extinction coefficient profile based on lidar data,the aerosol vertical extinction coefficient profile is used to calculate the aerosol scale height,and the relationship between the relative humidity and the aerosol scale height is explored.It is concluded that the aerosol scale height and relative humidity show a negative correlation,the higher the relative humidity,the smaller the aerosol scale height.2.Use the relationship between visibility and extinction coefficient to obtain the horizontal extinction coefficient near the ground;combine the surface extinction coefficient with the aerosol scale height to obtain the entire atmospheric aerosol optical depth.3.The aerosol scale height and optical depth in Hefei area in 2020 January and July were counted,and the relationship between the aerosol scale height and optical depth over time was obtained.Besides,the day and night trends and differences of the aerosol optical depth during the measurement period were obtained,and the aerosol optical depth was obtained.There are significant differences in the diurnal and night distributions,and the optical depth in day is greater than at night.In addition,the meteorological factors affecting the aerosol optical depth are analyzed,and it is pointed out that the aerosol optical depth and wind speed are negatively correlated.The greater the wind speed,the smaller the aerosol optical depth,and the aerosol optical depth and visibility show a negative correlation.The greater the optical depth,the smaller the visibility,and the correlation during the day is stronger than that at night.