Research On Detection Method Of Vertical Profile Of Cloud Condensation Concentration Based On Lidar

Atmospheric aerosol not only directly affect the balance of earth radiation by scattering and absorbing solar radiation,but also act as cloud condensation nuclei(CCN)to change the microphysical process of cloud.The study and analysis of vertical distribution characteristics of CCN is the key factor for quantitative analysis of aerosol cloud climate interaction.At present,CCN is mainly measured by ground and aircraft,which has the characteristics of low spatial-temporal resolution and high cost.Remote sensing technology can obtain high spatial and temporal resolution information of atmospheric parameters.Lidar has been widely used in atmospheric detection with its fine spatial-temporal resolution,long vertical detection range and stable continuous observation ability,which makes it possible to analyze the vertical distribution characteristics of aerosol and CCN.In this thesis,the retrieval technology of CCN vertical profile data using the lidar is studied.In order to obtain the vertical profile of CCN,the information of particle size distribution and hygroscopicity factor of aerosol is necessary,the thesis studies these key technologies.The correct retrieval of particle size distribution and the detection of hygroscopicity factor of aerosol are the premise of obtain CCN concentration.Based on the five optical parameters(two extinction coefficients and three backscatter coefficients)measured by multi-wavelength lidar system,the aerosol particle size inversion technology based on principal component analysis algorithm is studied.The error data of aerosol particle size distribution of different models are analyzed.The results show that the algorithm can realize the stable inversion of particle size distribution of aerosol and microphysical parameters of aerosol and the anti-noise performance of the algorithm is analyzed,and the stability of the algorithm are verified.In order to further verify the applicability of principal component analysis in cloud base particle size distribution inversion,the variation of aerosol distribution with height is simulated,and the relative error data is calculated and analyzed.The results show that the algorithm performs well in particle size distribution of cloud base.The calculation method of evaluating aerosol hygroscopicity using lidar data is studied,and the scheme of parameterized aerosol optical parameter growth factor is constructed,and the hygroscopicity parameters characterizing aerosol hygroscopicity are obtained by fitting.On the basis of aerosol particle size distribution and hygroscopicity growth factor,the inversion method of CCN concentration was studied.The CCN number concentration was calculated according to the aerosol particle size distribution and critical particle size obtained by inversion,and the vertical distribution of aerosol and CCN was studied.The results show that the effective radius,volume concentration and number concentration of particles increase with the increase of cloud height;The vertical distribution profile of CCN is in good agreement with of aerosol.The concentration of aerosol and CCN increased because of the influence of high relative humidity at the cloud base.