登陆热带气旋长久维持与迅速消亡的大尺度环流特征

THE DIAGNOSTIC ANALYSIS ON THE CHARACTERISTICS OF LARGE SCALE CIRCULATION CORRESPONDING TO THE SUSTAINING AND DECAYING OF TROPICAL CYCLONE AFTER IT’S LANDFALL

中文关键词:  登陆TC  动态合成  维持  衰减  大尺度环流

英文关键词:Landfalling tropical cyclone  Dynamic composite  Sustaining  Decaying  Largescale circulation

中文摘要:

      采用动态合成分析方法,对登陆后长久维持热带气旋(LTC)和迅速消亡热带气旋(STC)的大尺度环流特征进行合成分析和动力诊断。研究表明:(1)LTC登陆后,在一个长波槽前有向偏北移动靠近中纬度斜压锋区的趋势,而STC登陆后,无长波槽靠近,并远离中纬度斜压锋区;(2)LTC登陆后,仍与一支低空急流水汽输送通道连结,而STC登陆后很快与这支水汽通道分离;(3)LTC登陆后逐渐变性,获取斜压能量,其环境风垂直切变增强,Δζ_200-850负值增大,而STC登陆后没有这样的特征;(4)LTC登陆后,其高层与中纬度急流靠近,增强了其向东北方向的高空流出气流,而STC不存在这样一支流出气流;(5)LTC登陆后,摩擦使其能量耗损,但从中高层环境中获得了能量,而STC登陆后,有同样的能耗却无明显的环境能量补给。因此,当一个热带气旋登陆后,从其移动趋势、与水汽通道的连结、与斜压锋区的关系和高空流出气流等特征,可以初步判断其是长久维持还是迅速衰减。

英文摘要:

      The characteristics of landfalling tropical cyclones are quite different. Some of them would quickly dissipate (0-24 hours, refer to STC) right after they made landfall while others would be sustainable over land for a longer period (3-5 days, refer to LTC) after they made landfall. Statistical analyses demonstrated that the severe calamities were closely related to those typhoons which were sustained over land for longer time period. Dynamical and diagnostic analyses were employed in this study with compositedat a of 7 cases of LTC and 7 cases of STC. The different characteristics of the large scale circulation for these two categories of landfalling tropical cyclones are found. The results have shown that the lower layer moisture channel connect with the tropical cyclone circulation or the landfalling tropical cyclones move to wards north and gain the baroclinic energy from the mid-latit udejet that were favorable to sustaining of a tropical cyclone over land. The vertical shear of the wind would be increased in this process. A landfalling tropical cyclone might be sustainable over land for a longer time if the upper levere envolope of the landfalling tropical cyclone linked with a mid-latit udejet to enhance the upper level out flow tow ards northeast or the cyclones moved. into an area under an upper level strong divergent field. On the ot her hand, friction dissipation effect of a ground surface would consume the energy of a landfalling tropical cyclone and results its decaying. The energ y budget calculation suggested that the long sustaining tropical cyclones would acquire Kinetic energy from the mid-latitude environment when they moved north ward approach the west erlies while short sustaining tropical cyclones would not gain the energ y from the environment. They would be dissipated by the frictional consuming. The results of this paper could help the operational forecast on the sustaining of a tropical cyclone over land after it made landfall.