摘要
利用常规观测资料及NCEP 1°×1°6 h再分析资料,对2007年7月上旬四川东北部连续出现的3场大暴雨过程的环流形势及动力结构、水汽输送和热力不稳定条件进行了诊断分析。结果表明:(1)前2场区域性大暴雨出现在副热带高压和巴尔喀什湖冷涡两个长波系统稳定少动的阻塞环流形势下,第3场局地性大暴雨发生在环流调整过程中,副热带高压快速东撤导致对流云团在东移过程中迅速减弱消亡;(2)暴雨的水汽主要来自南海,低空偏南风急流的维持为连续暴雨提供了源源不断的水汽输送和持续的能量供应,3场暴雨的中心均出现在位于低空急流出口区左侧水汽辐合中心的巴中地区;(3)造成严重洪涝灾害的前2场区域性大暴雨过程期间,从地面到高层形成了"辐合—辐散—辐合—辐散"接力式上下大气运动的动力结构,大气层结处于高能和对流不稳定状态,且有冷空气触发,大暴雨发生在能量锋区偏向暖区一侧。
NCEP 1°×1° 6-hour reanalysis data are used to analyze the circulation pattern, the dynamic structure, the water vapor transport and the thermal conditions of 3 continuous heavy rainfall events occur in early July, 2007 in northeastern Sichuan province. The results are as follows： （1） the former two regional heavy rainfalls occurred under the stable block situation with two long-wave systems of subtropical high and cold vortex over Balkhash Lake, the third local heavy rainstorm occurs in the general circulation in adjustive course which subtropical high fast retreating eastward results in the convective clouds rapidly dissipating during eastward moving; （2） water vapor of rainstorms mainly are from South China Sea, the low-level south wind jet stream supplies water vapor and energy to persistent rainstorms successively, and the centers of the three rainstorm events are in Bazhong that is the water vapor convergence center at left side of lowlevel jet stream exit; （3） the former two regional heavy rainstorms which led to severe flood disaster, from low-level to upper level, is formed with convergence-divergence-convergence-divergence dynamic structure, the convective instable atmospheric stratification with high energy is triggered by cold air, and the heavy rainstorms are at the warm side of energy front.
出处
《暴雨灾害》
2008年第3期231-236,共6页
Torrential Rain and Disasters
基金
国家自然科学基金项目"青藏高原低涡切变线形成维持机制研究"(40775032)资助
关键词
暴雨
副热带高压
低空急流
动力结构
水汽输送
热力条件
Heavy rainfall
Subtropical high
Low-level jet stream
Dynamic structure
Water vapor transport
Thermal condition
