Abstract:Based on the historical surface synoptic maps for the period 1958-1989, the climatological analysis of the Altai lee cyclogenesis is presented. The Altai lee cyclogenesis area is the greatest in Asia. There are pronounced seasonal variation of the frequency of the lee cyclogenesis, the trend of the Altai lee cyclogenesis showed a decline from 1958 to 1977. The trend of pressure of the cyclogenesis showed a decrease from 1958 to 1989. A few Altai lee cyclones explosively deepen over the Japan Sea and the Pacific ocean.

Abstract:The machanism of the heavy rain occurred in the central and northern areas of Zhejiang Province, caused by the trough north of Typhoon 9021, has been inverstigated. The structure of the trough is analysed. Furthermore, the vertical velocity distribution around the cluster and the association with the heavy rain areas have been discussed. Finally,the mesoscale weather systems, from the ground to the upper level,around the cloud cluster have been also studied.

Abstract:Cumulus seedable degree during summer-autumn in Hunan Province is simulated by a constant one-dimension model of cumulus cloud. The results show that the average rates of cumulus seedability and rain enhancement are 75% and 55% respectively, which indicates the potention of weather modification and provides a reference for practical seeding clouds in Hunan.