影响台风移动因子的数值研究

本文采用有辐散的正压原始方程模式对影响台风涡旋移动的因子进行了数值试验,试验结果表明:(1)在无环境风条件下,台风涡旋向西北方向移动,移速与台风切向风速、台风半径和台风区f场的特征有关,台风外区(指最大风速半径以外台风区域)切向风速越大、台风半径越大,台风涡旋移速向北分量越大。(2)均一环境风场中,台风移动受基本气流的平流、β效应和指向引导气流左侧的横向加速度的作用,其中基本气流的引导作用是主要的。台风移速与引导气流速度比在东风气流中要大于西风气流中,而台风移向与基本气流之间的偏角在西风气流中要大于在东风气流中。(3)台风涡旋有沿基本气流绝对涡度梯度方向的次级运动分量。(4)台风涡旋在有切变的西风气流中比在均一西风气流中易发展加强,而它的移动更偏向引导气流的左侧。 

A NUMERICAL STUDY OF FACTORS AFFECTING THE MOTION OF A TYPHOON VORTEX

Numerical experiments of factors affecting the motion of a typhoon vortex have been made with a divergent barotropic primitive equation model,the results of which show that:(1) Provided that there is no environmental wind,the typhoon vortex would move northwestward at speeds relevant to the tangential velocity,storm radius and f field patterns,The greater the outer tangential velocity(outside of the radius of maximum winds) and the typhoon radius,the greater the north component of the vortex motion uill be. (2) Under the condition of uni-form environmental winds,the typhoon movement is subject to the advection of the basic flow. β effects and transverse acceleration to the left of the steering flow,which is the dominant force. The speed ratio between the storm vortex and steering flow is larger in the east flow than in the west flow while the vortex direction deviates more from the basic flow in the west flow than in the east flow. (3)The vortex has a secondorder dynamic component in the direction of the gradient of absolute vorticity of the steering flow. (4)It is easier for the typhoon vortex to deepen in a west flow with shear than in a uniform west flow,so that it moves more to the left of the steering current.