守恒系统中台风强度变化及其可能因子的数值研究

用一个高分辨率的 f平面正压涡度方程模式 ,实施了时间积分为 36h的 2 1组试验 ,研究相邻中尺度涡旋与台风涡旋的相互作用。结果指出 :这种相互作用能否导致台风加强 ,取决于两类因子 :一是台风涡旋最大风速的取值以及圆形基流切变的强弱 ;二是切变基流中的中尺度涡旋的自身条件 ,包括中尺度涡旋的分布、尺度、强度和结构。台风强度与初始中尺度涡旋的尺度、强度之间存在着非线性的联系

A NUMERICAL STUDY ON THE CHANGE OF TYPHOON INTENSITY AND ITS POSSIBLE FACTORS WITHOUT FORCING AND DISSIPATION

By using an f-plane barotropic quasigeostrophic model with the grid space being 5 km, twenty one experiments whose integration times are 36 h are performed in order to investigate the interactions between a typhoon vortex with the radius of maximum tangential wind equal to 100 km and adjacent mesoscale vortices which are located in the outer region initally. The distance between two centers of typhoon and mesoscale vortex is 200 km. Results show that whether the interaction can result in the typhoon intensification depends on two kinds of factors, one of them is the condition of the typhoon circulation, which contains the velocity maximum and the shearing of circular basic current, the other is the self condition of the mesoscale vortices, which contains the distribution, horizontal scale,intensity, and structure of the vortices. The favorable circumstances for the vorticity propagation from the outer region to the inner core and the intensification of the typhoon vortex are as follows:(1) The coexistence of both strong basic current, and strong shearing of typhoon circulation. In this condition, the vorticity propagation of the mesoscale vortex located initially in the northwestern quadrant to the inner core is very obviours, but in the case of strong current and weak shearing it falls into decay. (2) The asymmetric distribution of mesoscale vortex in the typhoon circulation. in this circumstance, the vorticity propagation can approach to the typhoon center, but when four same mesoscale vortices are located initially in the four quadrants respectively, exhibiting a symmetric pattern, it only can get into the places where the distance from the typhoon center is 100 km approximately. (3) Appropriate space scale and intensity of the mesoscale vortices. If the initial radius is larger than a critical scale, and the initial intensity is stronger than a critical value, the vorticity propagation may be remarkable. Some nonlinear relations between the typhoon intensity and the horizontal scale or the intensity of the initial mesoscale vortices can be exhibited.