对南海热带气旋近海加强机理个例模拟研究

A CASE SIMULATION STUDY ON OFFSHORE INTENSIFICATION MECHANISM OF TROPICAL CYCLONE IN SOUTH CHINA SEA

中文关键词:  热带气旋，加强，涡旋Rossby波，轴对称化

英文关键词:Tropical cyclone, Intensification, Vortex Rossby wave, Axisymmetrization.

中文摘要:

      利用具有完备物理过程的中尺度模式MM5对发生于南海的0214号热带气旋（TC）“黄蜂 ”进行高分辨率的数值模拟，以此来研究热带气旋在近海发展为强热带风暴过程中结构变化对强度的作用，并对近海加强的内部动力机理做一些探讨。模拟结果发现在加强阶段，气旋 环流中存在类似于涡旋Rossby波性质的波动在西北侧对流激发下绕中心逆时针传播，波动 与眼墙区对流带相耦合，使得眼区趋于闭合；中尺度涡旋系统的轴对称化过程，通过与对称环流系统非线性相互作用，向气旋环流提供能量，其自身也得到维持与发展。这些结构的变化对TC近海加强和登陆后迅速减弱都产生了重要的影响。

英文摘要:

      Full physical model MM5 has been used to simulate tropical cyclone “Huang Feng ” in August 2002. Adapting high resolution grids, the effect of structure chang es on intensity in the process of intensification was investigated. The simulati on catches evolution details to support further analysis.During the process of intensification, there exist two different synoptic syst ems in the two sides of TC circulation. One is deep subtropical high, which stre tches westwards and led adequate vapor into inner core; the other is cold votex located in the west of TC, which induced cold air to surrounding of TC circulati on through middle level to increase instability. These environmental conditions were favorable for TC intensification.According to vortex Rossby waves (VRW) theory to explore the mechanism of TC in tensification, the results confirm that there exists Vortex Rossby like waves, which are initiated by convection as perturbation source in the northwest of TC circulation. Vortex Rossby waves, coupled with eyewall convective band and spir al rain band outside, propagate cyclonically in the process of intensification. Ultimately the propagation of waves leads to form a complete eye structure in th e minimum botton of sea level pressure. Mesoscale vortices axisymmetrization ar e found to transfer energy to parent vortex through nonlinear interaction. Meant imevortices also experience self maintain and development process. These facto rs impact on the offshore intensification. After landfall, vapor channel is cut off and cold air penetrates low level to strengthen stability of troposphere. These unfavorable conditions weaken the convective activity and lead to decay of TC intensity.