Aerosol Extmction-Depolarization Obscrvatiori And Its Correlation Study

In this paper, the aerosol properties in northern subsurb of Nanjing is measured regularly by two laser radars: Raman-Rayleigh-Mie Lidar and Micro-pulse lidar of Nanjing comprehensive observation base of China Meteorological Administration.The paper introduces the detection principle,instrument parameters and data correction method of two lidars. Using the data of Rayleigh-Raman-Mie lidar to caculated monthly extinction coefficient of the aerosol and analyzed the monthly variation of aerosol extinction characteristics. Using the data of Micro-pulse lidar to caculated the depolarization ratio and the extinction coefficient of the aerosol.Analyzing the aerosol of diurnal variation of extinction characteristics,the change of depolarization ratio before and after a rainfall and the relationship between the depolarization ratio and the extinction coefficient is analyzed under different weather conditions.When studying monthly variation of aerosol extinction characteristics we found:the extinction coefficient decreases with the increase of height, and the rate of decrease in the range of 1km-2km will be obviously changed; the curve below 2km is relatively smooth, but there will be large or small fluctuations above 2km. when the cloud is detected, the extinction coefficient will become larger; the average extinction near the ground in January, June, July, and December is larger than that other months. When studying diurnal variation of aerosol extinction characteristics we found: extinction coefficient is larger below 1.5km; the height of the boundary layer will change with the intensity of solar radiation and people's travel and the boundary layer height reached the lowest before dawn.When studying aerosol depolarization ratio changes before and after a rainfall we found: the overall aerosol depolarization ratio is small before the rain; aerosol will be uplifted by the enhancement of solar radiation after noon, the depolarization ratio below 2km decreased obviously and the cover height increased.When studying the correlation between the depolarization ratio and the extinction coefficient we found: at the same time,the variation trends of the two are the same on sunny and haze days, and are also the same when the ice clouds is detected, while the trends are opposite when the water clouds is detected.