Synthetic Analyses of An Extreme Heavy Storm Rain on the East Side of Qinghai-Xizang Plateau in Early Summer

An extreme heavy storm rain on the east side of Qinghai-Xizang Plateau in early summer of 2002 was analyzed. The result showed that the cause of heavy storm rain was the low trough in Xinjiang combined with the Plateau trough, and lead to the convergence of strong cold air and southwest airflow of warm and moist from Sichuan to Shaanxi on the east side of Qinghai-Xiang Plateau. The strengthening of westerly jet in upper level, forming of blocking high in Eastern China, strengthening and extending northward of the warm and moist southerly airflows in low level provide the advantageous conditions for heavy storm rain. The activity of meso-β-scale convective system before warm area of cold front directly cause local heavy storm rain, mesoscale convergence system in low level is closely related to the activity of meso-β-scale convective cloud cluster, timing and precipitation region of heavy storm rain. The especial structure of vertical distribution of divergence in mesoscale convective system, namely the double structures of convergence-divergence from lower levels of troposphere to upper level, has an important role in forming strong ascending motion and deep convective formation of heavy storm rain.