“8·16”辽宁特大暴雨多尺度特征分析

Analysis on Multi-scale Characteristics of a Torrential Rainstorm in Liaoning Province on 16 August 2013

利用常规观测资料和区域自动气象站、多普勒雷达、风廓线雷达、地基GPS水汽观测仪等非常规观测资料以及NCEP(1°×1°)再分析资料,对辽宁省清原县2013年8月16日特大暴雨过程的多尺度对流系统特征进行分析。结果表明:低涡切变线和东北低压是本次暴雨过程的主要影响系统。700 h Pa与地面之间假相当位温差达43 K,表明大气强烈的对流性不稳定结构。850 h Pa辽宁大部分地区比湿达14 g·kg^(-1),比湿大值区存在明显的水汽通量辐合,沈阳站监测到的大气可降水量达55 mm,可见本次过程水汽充沛。5次雷达回波依次经过清原地区形成"列车效应",导致该地区特大暴雨。地面辐合线触发的对流单体受其两侧风场的强弱影响,中低层西南风的加强有利于加大新生单体的垂直风切变和水汽条件。短时强降水导致的冷池与其周边暖气流交汇可能触发新的对流单体。在地形影响下,中-β尺度云团和α云系合并过程中的微物理作用可能是导致强降水的主要原因之一。

Based on conventional observation data, unconventional observation data from regional automatic weather stations, Doppler and wind - profiler radar as well as ground - based GPS, and NCEP reanalysis data with 1°× 1° spatial resolution, the multi - scale convective characteristics of a torrential rainstorm on 16 August 2013 in Qingyuan county of Liaoning Province were analyzed. The re-sults show that the low vortex shear line and low pressure in Northeast China were the dominant dynamic systems during the rainstorm process. The difference of pseudo - equivalent potential temperature between 700 hPa and ground was 43 K, which indicated the strong instablility of atmospheric stratification. The specific humidity on 850 hPa over most areas of Liaoning Province reached 14 g · kg︿-1, the vapor convergence was obvious in high specific humidity region, and the atmospheric precipitable water over Shenyang from GPS was 55 mm, so the vapor condition in the process was abundant. Five radar echoes went through Qingyuan region in turn, and formed “train effect”,which caused the heavy rainfall. The surface convergence line triggered new convective cel ls, and the intensity of wind fields in two sides of the convergence line affected the moving direction and speed of new convective cells. Moreover, the enhancement of southwesterly winds at middle and low levels was beneficial to improve the instability and moisture conditions. In addition, the inter-section between the cold air in cold pool caused by short - time strong rainfall and the surrounding warm airflow might trigger new con-vective cells. Under the influence of terrain, the microphysical interaction in the process of merging between the meso -β scale cloud cluster and a cloud system might play an important role to produce the strong rainfall.