Research On The Microphysical Structure Characteristics Of Stratiform Warm Clouds And The Threshold Function Of Automatic Transformation Of Cloud And Rain In Jiangxi Region

In order to deeply study the microphysical structure characteristics of stratiform warm clouds in Jiangxi Province,the difference of microphysical structure between precipitation and non precipitation stratiform warm clouds,and the cloud-rain autoconversion threshold function(T),we analyzes the microphysical properties of precipitating and non-precipitating warm cloudsbased on seven-flight cloud measurements from November 6 to December 25,2014,in Jiang Xi Province,China.At the same time,through the calculation of T value of stratiform warm clouds,we discuss the influence of the automatic transformation process of cloud and rain on the micro physical quantities,especially the dispersion effect,and analyze the possible mechanism of the formation of the correlation between?and N_c,and the interaction between aerosol and automatic conversion function of cloud and rain is studied to enhance the understanding of the interaction between aerosol,cloud and precipitation.By Comparing the vertical distribution characteristics of microphysical parameters and droplet size distribution in precipitation cloud and non precipitation cloud,it is found that the LWC and ED of precipitation cloud and non precipitation cloud increase gradually with the height,and the LWC of precipitation cloud is larger than that of non precipitation cloud,which indicates that updraft plays an obvious role,and precipitation cloud develops vigorously compared with non precipitation cloud.The concentrations of the two kinds of clouds are higher in the small cloud drop section,and the N_cdecreases with the increase of the particle size.The large cloud drops in the precipitation cloud are mostly in the upper layer of the cloud.It is found that the probability distributions of N_c,LWC and ED of precipitation cloud and non precipitation cloud are unimodal,but the average and standard deviation of micro physical parameters of precipitation cloud are higher than those of non precipitation cloud,which indicates that precipitation cloud is more vigorous than non precipitation cloud.The autoconversion threshold function(T)represents the probability that the collision-coalescence process occurs in clouds,which is critical to determine the initial time and intensity of the precipitation.We found that,in general,the T increases with height above the cloud base,with the maximum value occurring in the middle and upper parts of clouds.The occurrence frequency with T>0.6 in the precipitating clouds is larger than that in the non-precipitating clouds,indicating a stronger collision-coalescence process and a greater probability of raindrops generated by the condensation and collision-coalescence processes in the precipitatng clouds.There is a negative relationship between the relative dispersion of?and N_c;meanwhile,the negative relationship becomes more evident with the increasing T.Compared with the average radius of cloud droplet(r_a),the standard deviation of cloud droplet size distribution(?)dominates the enhancement of the degree of the negative relationship between?-N_c.The frequency of T value below 0.4 in polluted conditions is much higher than that in clean conditions,because indirect effect of aerosol makes the number of cloud droplets increase and the radius of cloud droplets decrease,which inhibits the automatic transformation process of cloud and rain in stratiform warm clouds.