Observation Research on Cloud Microphysics and Precipitation Affection of Stratiform Cloud Seeding by Liquid Carbon Dioxide

The detail information is deduced on the microphysical affection of stratiform cloud seeding,including in situ aircraft measurements,radiosondes,radar data,and surface observations in the experiment of precipitation enhancement in Jilin Province during 11-12 July 2002.The results indicate that the maximum of cloud super cooled liquid water content reaches 0.1-0.2 g/m~3,but the concentration of ice crystal is very low for nature cloud.It means that the cloud is eligible for precipitation enhancement seeding according to principle of weather modification.The changes of cloud microphysical structure,such as the increasing of ice crystal concentration and diameter of rain droplets,the decreasing of super cooled liquid water content,are caused by seeding liquid CO_2.The increase in radar echo intensity in the incidence area comparing with the target area is also caused by cloud seeding,which is similar to the increase in concentration of rain droplets observed by in situ aircraft.For the precipitation intensity in the incidence area of cloud seeding increases but it only slightly changes in the comparison area.The redistribution of rainfall is caused by cloud seeding in the precipitation area.