Abstract:Wide range of high temperature and drought occurred in South China in the summer of 2013. From 1 to 22 August, Weather Modification Center of CMA carried out the work of cloud structure forecast and seeding conditions analysis using weather modification models. This paper briefly reviews drought and weather and analyzes cloud structure forecast and seeding conditions. Three types of cloud system precipitation happened during 1-22 August in the drought region. Type I is precipitation of typhoon periphery cloud system from 1 to 4 August, Type II is precipitation of local convective cloud controlled by subtropical high from 5 to 13 August, and Type III is low pressure cloud system from 14 to 22 August after typhoon landing. The precipitation forecasts of weather modification model are basically correct with observations of Types I and III, but a bit different from Type II. The forecast results are validated by the observations of satellite, radar and precipitation. The distribution of large cloud system coincides with the retrieval result of satellite. The model can forecast the development of local convective cloud. The cloud property and vertical structure are basically consistent with radar observations. The seeding conditions are analyzed through the products of cloud band, supercooled water, vertical structure of cloud, precipitation etc. There is not only warm cloud but also mixed phase cloud of precipitation of Types I and III. The mixed phase cloud has supercooled water with the maximum of 0.3 g·kg-1 and less ice crystals between 0 and -10℃, which is suitable for cold cloud seeding. In the beginning stage there is the supercooled water with maximum value 1 g·kg-1, which is good for cold cloud seeding. A lot of work needs to do about the microphysical and seeding conditions of model forecasts for mixed phase cloud and precipitation in South China.