中纬度高空槽—台风相互作用对台风“利奇马”远距离暴雨的影响

利用NCEP提供的0.25°×0.25° FNL资料和国家气象信息中心提供的高分辨率三源融合降水资料,以台风"利奇马"为研究个例,从动力和热力因素两个方面研究了中纬度高空槽与台风之间的相互作用对台风远距离暴雨的影响。研究认为中纬度高空槽—台风的相互作用是此次台风远距离暴雨的主要原因之一。在高空槽—台风的相互作用中,随着弱正PV异常从中纬度高空槽向台风区域的水平平流,台风西北部地区逐步处于高空槽前西南急流的次级环流的上升区域,而对流层深厚的暖平流恰好位于台风西北部3~5个纬距的地区,此热成风暖平流的作用增强了台风西北地区的上升运动。另外,中纬度高空槽后的干冷空气的逼近,促进了在台风西北部地区的中纬度斜压锋生,斜压锋面进一步增强了台风远距离暴雨处的动力抬升作用。同时还发现当台风与中纬度槽的距离大约是10个纬距时其相互作用最为显著。

The interaction between the mid-latitude upper trough and typhoon on remote heavy precipitation of Lekima

By using the 0.25°×0.25° FNL data provided by NCEP and the high-resolution three-source merged precipitation data provided by National Meteorological Information Center, the interaction between the mid-latitude upper trough and Lekima (1909) on remote heavy precipitation was investigated involved dynamic and thermal processes. The interaction between the mid-latitude upper trough and Lekima (1909) is considered as one of the main reasons for the remote heavy precipitation. In the interaction between the mid-latitude upper trough and typhoon, the northwest of typhoon is gradually located in the ascending area of the southwesterly jet in front of the trough as the weak positive Potential Vorticity (PV) anomaly is advected horizontally from the mid-latitude upper trough to typhoon. The deep tropospheric warm advection is located in the area of 3°-5° to the northwest of typhoon, which enhances the ascending motion at the northwest of typhoon. In addition, the approach of dry and cold air behind the upper trough promotes the middle-latitude baroclinic frontogenesis at the northwest of typhoon, which further enhances the dynamic uplift of the typhoon at remote heavy precipitation area. Furthermore, the interaction between typhoon and mid-latitude upper trough is the most significant when their distance is about 10°.