重庆2014年9月12—19日连阴雨过程分析

Analysis on a Continuous Autumn Rain in Chongqing in 2014

利用NCEP1°×1°的再分析资料及重庆地区逐日、逐时降水资料、TBB资料以及雷达回波资料对重庆2014年9月12—19日连阴雨天气及期间两次暴雨过程进行对比分析。结果表明:此次连阴雨期间欧亚大陆中纬度为"一槽"型,暖湿气流沿台风"海鸥"外围以及副高边缘不断将南海及西太平洋的水汽输送至川渝地区,为连阴雨提供良好的水汽输送条件;比湿的演变对连阴雨期间降水的增强及间歇有明显的指示意义,负的整层水汽通量散度大值区与两次暴雨落区一致。连阴雨前期大气为对流不稳定层结,能量条件好,阻塞高压明显,中高纬度的环流经向度较大,有利于冷空气的快速南下,前期的"9·13"大暴雨的对流性特征更明显;后期"9·17"暴雨则表现为稳定性降水,TBB资料在连阴雨期间的强度演变对两次暴雨过程产生的时段和落区的指示意义较好。在整个连阴雨期间近地层多弱冷空气的影响,中层有偏南风,连阴雨天气得以持续,但是两次暴雨过程开始时,冷平流均有明显的增大,表明冷空气有所加强,冷空气的加强触发了暴雨的产生,同时伴有中层偏南暖湿气流的增强。从两次暴雨过程时多普勒雷达垂直风廓线图也能反映出低层冷空气入侵,中层偏南暖湿气流的增强。

Based on the 1°x 1°NCEP reanalysis data, daily and hourly precipitation observation data, TBB and radar data, a continuous autumn rain happened from September 12th to 19th of 2014 in Chongqing was analyzed. We also compared the similarities and differences in characteristics between the two heavy rainfall processes during the continuous autumn rain. The result showed that the geopotential height filed of 500 hPa was the “ one-trough” type during the continuous rain period. Moreover, the warm and wet air flowed along the periphery of the typhoon Seagull” or the edge of the WPSH（Western Pacific Subtropical High）, and transported the water vapor from the South China Sea or the Western Pacific to the Sichuan and Chongqing region, which provided enough water vapor for the two heavy precipitation processes. In addition, the specific humidity was a good indicator of precipitation intensity enhancement and temporary stop. In the early period of the continuous autumn rain, the atmospheric stratification was convective unstable and the energy for rainfall was abundant. Thus,the convective characteristics of the “9 ？13” rainstorm in that early period was more obvious. However,the “9＊ 17”rainstorm in the later stage of the autumn rain was stable precipitation. The TBB intensification evolution during the continuous rain period was a relatively good indicator of the two rainstorms. The weak cold air in the near ground layer and southerly wind in the middle layer sustained the continuous autumn rain. Both of the two rainstorms could be observed the increase of the cold advection at the beginning of the heavy rainfall process, which indicated that the cold air had been strengthened. The enhancement of the cold air, together with the strengthened southerly humid and wet flow in the middle layer, triggered the rainstorm. The vertical wind profile of Doppler Radar also showed these characteristics.