承德市一次由快速发展气旋诱发的大风天气分析

利用常规观测资料和NCEP/NCAR(1°×1°)逐6 h再分析资料,对承德市2017年5月5—6日大风天气的环流形势和物理量进行分析,结果表明气旋的快速发展(气旋加深率0.84 B)导致锋生加强,引发气压和变压梯度加大是导致大风的直接原因。500 hPa高压脊东移迫使冷空气向南堆积,高空槽不断发展成为冷涡,温度平流为地面气旋的发展提供热力条件,高低层涡度平流的差异,也是地面气旋快速发展的重要原因;当1.5 PVU位涡面伸展至对流层低层时,局地位涡异常在气旋的发展过程中不可忽视;高空急流出口区发生质量调整,出口区左侧的辐散强度达10×10~(-5) s~(-1),使低层大气减压,有利于气旋发展。

FENG Yu-bo,WANG Hong,YANG Mei,GAO Yan-chun

By using conventional observational data and 6 hourly NCEP/NCAR reanalysis (1°× 1°), the atmospheric circulation features and physical mechanisms of gale weaher in Chengde City on 5 to 6 May 2017 were analyzed. The results show that pressure gradient and allobaric gradient caused by the rapid developing cyclone which caused frontogenesis strengthening is the direct cause of gale weaher. Analysis of large-scale circulation and diagnostic analysis of the physical mechanisms such as temperature advection,vorticity advection,potential vorticity and upper-level jet stream show that temperature advection and vorticity advection are important to the cyclone development. Potential vorticity anomaly can lead to rapid development of cyclone. Divergence is beneficial to development of cyclone in the left of upper-level jet exit region front of trough.