我国飑线发生条件研究

利用常规观测、地面自动站加密观测资料、NCEP（0.25°×0.25°）再分析资料以及多普勒雷达资料等，对2016年9月24日发生在内蒙古东南部一次致灾飑线天气过程进行分析。结果表明：（1）中高层干冷空气扩散东南下与低层西南急流的辐合急剧加强为强飑线提供了非常有利的大尺度环流背景；（2）对流有效位能（CAPE）在强对流爆发前有明显跃升；假相当位温（θ_se）中低层分布呈显著的倒漏斗状，而且随高度增高递减率明显增大，这种上干下湿的层结有利于雷暴大风和冰雹等强对流天气产生；（3）地面中尺度露点锋（干线）和中尺度辐合线长时间维持、耦合并加强成为这次强对流天气的直接触发和维持机制；飑线后部一直维持雷暴高压，表明有地面大风存在；（4）雷达回波伴有弓形回波特征，低层呈现有界弱回波区（BWER），中高层有明显的回波悬垂，50~55 dBz强回波区延伸到7.5 km，表明对流风暴内有强烈的上升气流，有利于短时强降水和大冰雹的形成；（5）弓形回波径向速度剖面图上存在中层径向辐合（MARC）。

The distinction between large-scale and mesoscale contribution to severe convection:A case study example

Based on the conventional observation data, automatic weather station data, Doppler radar data and NCEP(0.25°×0.25°) reanalysis data, a strong convective weather event occurred in the southeastern Inner Mongolia on 24 September 2016 caused by the disaster squall line was analyzed. The main conclusions are as follows. In the high and middle levels, cold and dry air masses spread to the southeast with the convergence of the low southwestern jet drastically strengthened, which provides this strong squall line process a very good large-scale circulation background. The CAPE has a significant increase before the strong convective weather occurred. The middle and low level distribution of θ_se presents like inverted funnel, and decreases with the increase of the height. This kind of dry and wet structure is favorable for the occurrence of strong convective weather such as thunderstorms and hails. The direct trigger and maintenance mechanism of this strong convective weather are due to the longtime maintaining, coupling and increasing between ground scale dew point front(dry line) and mesoscale convergence line. The thunderstorm high pressure stayed after the squall line indicating that there is a surface strong wind. The characteristic of radar echo appears like bow echo. The reflectivity profile of the bow echo front shows that there is a boundary weak echo region(BWER) in the lower layer. In the high-level, it has obvious echo drape. Strong echo zone achieve 50-55 dBz extends to 7.5 km, indicating that a strong upward flow is in the convective storm which is conducive to the formation of short-term heavy rainfall and the large hail. The arcuate velocity profile of the bow echo represents a strong sinking airflow and the middle ground radial convergence (MARC) of the ground wind warning index.