陆地上爆发性温带气旋的暖锋后弯结构分析

尽管关于温带气旋发展和演变的观点不尽相同，但目前普遍被接受的两种模型是：挪威气旋模型、Shapiro和Keyser模型。以FY-2E卫星云图为基础，先给出8个温带气旋过程实例，然后结合常规高空、地面观测及NCEP的1°×1°再分析场等资料，通过个例分析，对暖锋后弯气旋发生发展的环流背景、结构及成因进行分析。结果表明：(1)卫星云图显示东亚陆地上温带气旋存在T-bone结构和暖锋后弯的事实。(2)温带气旋发生在500 hPa东亚大陆中高纬两脊一槽的背景下，槽加深及下游脊的发展有利于气旋的发展，与经典温带气旋发生发展的环流背景类似。(3) 2012年5月11—13日个例分析表明蒙古气旋中存在锋面波动、锋面断裂、T-bone结构和暖锋后弯、暖核被隔离现象；暖核可从地面向上伸展到600 hPa。(4)在地面气旋初生和发展阶段，地面气旋中心西侧高低层正相对涡度区呈后倾结构；当高低层正涡度区几乎垂直重合时，地面气旋停止发展；气旋中心西侧对流层中低层的锋区一直存在。(5)当高低层涡度平流差值为正、300 hPa正涡度平流引起的辐散叠加到对流层中低层锋区之上，地面气旋才会生成和发展。逐渐增强的暖平流从气旋中心的东部和北部向气旋的西部和西南部输送，从而形成了卫星云图上的T-bone结构和暖锋后弯现象。

On the structure of moving cyclones

Although there are many different views on the formation and evolution processes for extratropical cyclones, the classical Norwegian cyclone model and Shapiro-Keyser cyclone model are commonly accepted. Based on FY-2E satellite images, 8 extratropical cyclone cases were studied. Then, the background, the frontal structure and mechanism of cyclones were analyzed using conventional observations, and NCEP 1°×1° reanalysis data. The results indicate the following. (1)The back-bent warm fronts of extratropical cyclones were found over East Asian land from FY-2E satellite images. (2) The extratropical cyclogenesis with back-bent warm front occurred under the conditions of a trough and ridge downward had developed at 500 hPa. This background is the same as that for a classical cyclone. (3) Four stages, such as incipient frontal cyclone, frontal fracture, frontal T-bone and bent-back front, frontal T-bone and warm seclusion were observed in the extratropical cyclone that occurred on 11-13 May 2012, and its warm core extended up to the 600 hPa level. (4) During the development of the surface cyclone, the positive vorticity centers tilted rearward with height. While weakening, they were vertically overlapped at different levels. There were frontal zones in the low-middle troposphere. (5) It was also found that cyclone would develop when the differential vorticity advection between 300 hPa and 700 hPa was positive, and the divergence caused by positive vorticity advection at 300 hPa was located above the warm advection at 700 hPa. Back-bent warm front of extratropical cyclone was accompanied by strong warm advection which were conveyed westward and southward at 700 hPa.