垂直风切变对螺旋波不稳定的影响  

The impact of vertical wind shear on spiral wave instability

作　　者：刘琳[1] 张铭[1] 

机构地区：[1]解放军理工大学大气环流与短期气候预测实验室,南京211101

出　　处：《气象科学》2010年第2期158-163,共6页Journal of the Meteorological Sciences

基　　金：国家自然科学基金项目(40905021);上海台风研究基金课题<螺旋云(雨)带的形成机制及其与台风强度变化的关系研究>

摘　　要：通过建立一系列局地准二维直角坐标系,用以研究垂直风切变对热带气旋中螺旋波不稳定的影响,并计算了螺旋波不稳定增长率在螺旋线上的分布,得到了以下结论:不稳定增长率开始随热带气旋半径增大而增大,在最大风速圈处达最大;然后随半径减小,以后再随半径增大,出现一个局地极值,再以后又减小,即在螺旋线上有两个极值中心;这与实际热带气旋的情况相一致。不稳定螺旋波的增长率与基流的垂直切变和层结参数密切有关,基流垂直切变越大,层结参数越小,则增长率越大;也即Richardson数越小,则不稳定增长率越大。In this paper we use a series of local quasi-two-dimensional Cartesian coordinates to study the impact of vertical wind shear on spiral wave instability in tropical cyclones, and calculate the distribution of the growth rate of spiral wave instability on the spiral line. The conclusions are as follows ： at the beginning, the growth rate of instability increases as the tropical cyclone radius extends, and became the largest on the maximum wind-speed circle; then it decreases later and goes up again when it gets a local extreme value. That is to say, there are two maximums on the spiral line; this is in accordance with the actual situation of tropical cyclones. The growth rate of spiral wave instability is closely related to the vertical shear of the basic flow and stratification parameter. The greater the vertical shear is, or the smaller the stratification parameter is, the greater the growth rate is; that is to say, the smaller the number of Richardson is, the greater the growth rate of instability is.

关 键 词：热带气旋 风垂直切变 螺旋波 不稳定 

分 类 号：P444[天文地球—大气科学及气象学]