九岭山地形对弓形飑线形成影响的模拟分析

基于GSI-3DVar同化系统，将多部多普勒雷达径向风和反射率资料同化进入初始场，利用WRF-ARW模式对2016年4月16日发生在江西省西北部的一次飑线天气进行数值模拟，以分析九岭山地形对飑线形状演变的影响及其原因。结果表明：1） 真实地形下的试验基本再现了飑线在经过九岭山东移下山过程中由直线形演变成弓形的情景，而将地形高度减半后飑线未能由直线形演变成弓形，地形直接影响了飑线形状的演变。2） 九岭山地形影响飑线系统的近地面冷池和后侧入流急流的强度，其中九岭山地形存在时，气流下山增强，飑线后侧对流层低层形成强后侧入流急流，且形成近地面冷池，有利于飑线由直线形演变成弓形。若九岭山地形不存在时，后侧入流急流明显减弱，近地面冷池强度也有所减弱，飑线未能由直线形演变成弓形。

Orographic Impact of Jiuling Mountain on the Formation of a Bow-Shaped Squall Line

The radial velocity data and reflectivity data from multiple Doppler radars were assimilated by the Community Gridpoint Statistical Interpolation (GSI) assimilation System, a squall line occurred in Jiangxi province on 16 April 2016 was simulated using WRF-ARW model, to analyze the orographic impact of Jiuling Mountain on the evolution of the squall line. The results showed the experiment with real orographic could reappear the process that the straight squall line gradually evolved into a bow shaped squall line when it went eastward down through the Jiuling Mountain, but when the terrain height halved the straight squall line could not evolve into a bow-shaped squall line, so the topography directly impacted the evolution of the squall line shape. The topography of Jiuling Mountain affected the intensity of the surface cold pool and the rear inflow jet of the squall line system. As Jiuling Mountain existed, the airflow enhanced when it went downed through the mountain, and strong rear inflow jet formed in the lower troposphere back of the squall line, and then cold pool formed, which were both conductive to the evolution process of a straight squall line into a bow shaped one. If Jiuling Mountain did not exist, the intensity of the rear inflow and cold pool weakened, and the straight squall line would not evolve into a bow-shaped squall line.