The preliminary syudy of medium-scale cloud clusters over the Changjiang basin in summer

It is shown that the medium scale cloud cluster is u major one of precipitation systems from analysing the rainstorms along the Changjiang River during the plum rain period of 1980-1983. The medium-scale cloud clusters do not always correspond to the moving vortex, but they are in good agreement with the convergence center for the divergent component of wind at 850 hPa. The favourable environmental conditions for the genesis and development of medium-scale cloud cluster, such as the large-scale circulation situation, patterns of temperature and moisture, potential instability, and the structure of cloud cluster are given. A model on large seaie clond pattern for the genesis of medium scale cloud cluster is presented.