应用日本气象厅1979~2008年的热带气旋资料以及日本25年 (JRA-25) 再分析资料, 本文首先对登陆我国变性加强和变性减弱的两类热带气旋进行了合成对比分析, 发现热带气旋变性后的强度变化与相应的西风带高空槽的强弱有很好的对应关系。然后, 我们选取了2004年登陆我国的热带气旋Haima为研究对象, 通过中尺度模式模拟再现了其登陆后变性演变过程, 采用片段位涡反演方法改变了模式初始高空槽的强度, 研究了高空槽强度的变化对Haima变性过程的影响。研究表明: (1) 高空槽加强 (减弱) 后, Haima移速明显加快 (减慢), 此外深 (浅) 槽对应的Haima变性加强过程中心气压降幅较大 (小); (2) 不同强度的高空槽与Haima相互作用的过程中, 深槽对应的高空急流范围较大, 强度更强, 相应的高空强辐散有利于Haima明显的再发展; (3) 另外深槽对应着较强的高层正位涡带, 正位涡向下伸展诱发低层Haima正位涡明显增长, 从而导致低层锋区的强烈发展和低层气旋的明显加强。
Based on the Tropical Cyclone (TC) data and Japanese 25-year reanalysis data of Japan Meteorological Agency from 1979 to 2008, compositing and comparative analysis was firstly performed to study the intensifying and weakening TC during the Extratropical Transition (ET) over China.The analyses reveal a nice corresponding relationship between the variation of TC's intensity after ET and initial strength of the westerly upper-level trough. Then TC Haima which made landfall on China in 2004 was taken as an example, the evolution of its transition process was reproduced by the mesoscale atmospheric model. The authors modified the intensity of upper-level trough in the initial fields using the method of piecewise potential vorticity (PV) inversion and investigated the impacts of different troughs on Haima's re-intensification process during ET. The results indicate that Haima moved quickly (slowly) when the trough enhanced (weakened), furthermore, the deeper (shallower) the upper trough is, the stronger (weaker) the Haima re-intensifies; the deeper trough shows wide and strong upper-level jet and enhanced divergence, which is favorable for Haima's redevelopment; besides, the deeper upper trough was accompanied by stronger positive belt of PV, the upper-level positive PV propagated downward to lower levels to result in the growth of Haima's positive PV and the intense development of low-level baroclinic frontal zone, finally, the low-level cyclone was reinforced obviously.
李侃,徐海明.西风带高空槽对登陆我国变性热带气旋的影响及其机理研究.大气科学,2012,36(3):607~618 LI Kan, XU Haiming. The Impacts of Westerly Upper-Level Trough on the Extratropical Transition of Tropical Cyclones Landing over China and its Possible Mechanisms. Chinese Journal of Atmospheric Sciences (in Chinese),2012,36(3):607~618复制