利用常规地面观测资料、区域站资料和NCEP逐6 h 1°×1°的再分析资料,分别从2次强降水过程的影响系统形成机制上做了对比分析。结果表明:第1阶段强降水的主要影响系统有高空槽、中低层切变线和低空急流,属于对流性降水过程;第2阶段强降水过程主要受高空槽、副高外围和低涡的影响,对流性和稳定性降水并存,同时对比发现水汽通量散度辐合中心能加强强降水的发生,低层正涡度和高层负涡度的上下配置更能造成强降水的发生。
Based on the NCEP reanalysis and conventional observation information,the circulation background and physical quantity field of the rare continuous intensive precipitation process occurred in autumn(from October 24 to November 5) of 2008 in central section of Yunnan Province were analyzed and diagnosed.The results showed that the low-level cold front shear and mid-high level convergence zone maintenance constituted the main synoptic situation background of the rare continuous heavy rainfall in autumn in the middle regions of Yunnan Province.The two water vapor which came from the Bay of Bengal and the south of Indo-China Peninsula converged in the central and southern Yunnan,forming a deep moisture convergence zone.The warm and humid air climbed upward along the low-level cold air with the formation of a long period of upward motion,playing an important part in the maintenance of heavy precipitation weather process.The continuous heavy rainfall center and the weak high values of convective available potential energy(CAPE) had good corresponding indexicality.During the heavy precipitation,there were five mesoscale clouds which generated in the cold wind shear cloud belt.In this favorable context of large-scale circulation,frequent movement of the mesoscale system was the direct cause of this continuous intensive precipitation process.