近10 a中亚低涡背景下新疆短时强降水环境场分析

Characteristic analysis of environment of short-time heavy rainfall under the background of the Central Asian Vortex in Xinjiang in recent ten years

为更好地把握中亚低涡造成新疆短时强降水天气过程的机理特征,为新疆短时强降水预报预警提供参考和依据,利用FNL资料、探空资料等,运用天气学原理、动力诊断分析方法等,研究了中亚低涡系统不同部位发生的三类短时强降水的环境场特征及环流配置。结论表明:(1)短时强降水发生在500 h Pa中亚低涡前部西南气流下为最多。(2)A指数在新疆地区短时强降水降水预报中意义不大。(3)中亚低涡背景下新疆短时强降水天气的配置一般属于高空冷平流强迫类。(4)三类短时强降水形势配置的共性:在低涡背景下,对流层中高层都有显著气流存在,低空有切变线存在,近地面往往有辐合线,700 hPa左右往往有湿舌。异性:第I类短时强降水湿度条件较好,第Ⅱ类短时强降水高低空温差较大,第Ⅲ类短时强降水垂直风切变较强。

The Central Asian Low Vortex often caused many anomalies such as short-time heavy rainfall, low tem- perature and drought in Xinjiang, China. In order to fully understand the mechanism how a short-time heavy rainfall in Xinjiang is generated under the background of the Central Asian Low Vortex and therefore to provide referential data for the forecast and early warning of a short-time heavy rainfall, this paper analyzed the environmental field characteristics and circulation configurations of three different kinds of short-time heavy rainfall caused by Central Asian Low Vortex in Xinjiang occurred from May to September between 2005 and 2014. Based on the principle of synoptic meteorology and dynamic meteorology, this study conducted the analysis using the observational data, NCEP FNL data and radiosonde data. The result indicates as follows ： （ 1 ） Most of the short-time heavy rainfalls are of the first type and took place in the southwest airflow in front of the low vortex of 500 hPa. The second type short-time heavy rainfalls come second and they took place in northwest airflow and the third type short-time heavy rainfalls as the least took place in west airflow. （2） The A index changes greatly without rules to follow. Therefore the A index makes no sense in precipitation forecast in Xinjiang. （3） The circulation configuration of the short-time heavy rain- fall under the background of Central Asian Low Vortex belongs to the pattern of convective weather caused by upper cold advection. （4） The common ground of the three types of short-time heavy rainfall in the circulation configura- tion is that there is significant airflow in the upper troposphere, shear lines in the low altitude and east wind conver- gence line near the ground, and moist tongue at 700 hPa. The difference of the three types of short-time heavy rain- fall existed in the circulation configuration. The first type rainfall has significant southwest airflow at 500 hPa and has big moist tongue. The second type rainfall has significant northwest airflow at 500 hPa with a big temperature difference between the high and low altitudes but humidity conditions in general. The third type rainfall has signifi- cant west airflow at 500 hPa with a strong vertical wind shear.