大别山地形对江淮飑线发展变化及组织结构的影响研究

利用中尺度WRF模式,NCEP/NCAR再分析资料以及常规气象观测资料,对2014年7月11—12日发生在江淮地区的一次飑线过程进行数值模拟、地形敏感性试验和对比分析,研究了在经过大别山地形时飑线内部组织结构的变化特征以及地形对其发展的影响。结果表明:(1)飑线经过大别山主体时在山前加强以及过山后迅速减弱的主要原因与山前对流不稳定、上升运动大于山后有关;(2)大别山东部边缘对飑线的加强有增幅作用:当午后飑线移至大别山东部边缘时,东部边缘的谷风加强并强迫对流单体在飑线的前部新生,试验得出谷风可使低层风速最大增强6 m·s~(-1)左右,若无山谷存在时前向新生单体不再出现;(3)经地形敏感性试验得出:地形引发的大别山东部背风一侧的背风波扰动,有利于飑线内部对流单体的发展与加强,同时充沛的水汽补充,也是下山后飑线加强的因子之一。

Study of the orographic effects of the Dabie mountain on the development and structure of squall line

By using the WRF model, NCEP/NCAR reanalysis data and conventional meteorological observation data, a squall line process occurred in Jianghuai region during 11-12 July, 2014 was conducted numerical simulation, topographical sensitivity experiments and comparison analysis. Moreover, the variation characteristics of inner organizational structure of the squall line and the orographic effect on the squall line when went through the Dabie Mountain were also studied. Results show that:(1) the reasons why the squall line strengthened in front of the mountain and while weakened rapidly at the leeward side are the instable windward convection and the much stronger upward movement. (2)The eastern edge of Dabie Mountain had a greater contribution to the strengthening of the squall line. When the squall line moved to the Dabie Mountain in the afternoon, the valley wind circulation strengthened at the eastern edge and it forced the convective cell generate in the front of the squall line. The experiment shows that the valley wind can enhance the low-level wind velocity up to 6 m·s^-1. There existed no new cell without the valley wind. (3)Sensitivity experiments implied that the lee wave turbulence at the east side of Dabie Mountain caused by the terrain is conducive to convective development and the strengthening of squall line. Furthermore, the supplement of abundant moisture is one of the factors to the strengthening of the squall line when it went down the mountain.