1822号台风“山竹”的涡旋Rossby波特征分析

采用WRF中尺度模式对2018年22号台风“山竹”进行高分辨率的数值模拟，在此基础上，分析台风的精细动力结构和雨带特征。分析结果发现，台风“山竹”的眼墙处具有低层辐合流入、高层辐散流出的动力配置；台风眼墙附近存在切向风速的高值区和明显的垂直上升区，并且随着高度逐渐向外侧倾斜，同时该处的雷达回波也较强，对流系统较为深厚。然后利用尺度分离方法得到涡旋罗斯贝(Rossby）波的扰动场，进一步分析了台风“山竹”内部的涡旋Rossby波特征。研究发现：1）1波和2波会同时沿着切向和径向方向传播，2波的振幅明显小于1波；1波和2波的正涡度扰动大值区基本覆盖强的雷达回波区域，同时伴有较强的对流活动。2）垂直方向上，降水区的涡度扰动呈现出上层为正、下层为负的动力配置时，同时散度扰动的垂直方向也有类似配置时，则会加强对流系统的发展，有利于降水的增强。由此可见，1波和2波扰动的上层辐散下层辐合的动力配置会促使对流系统的加强，同时也会对台风降水的强度和分布有一定的作用。

Analysis on characteristics of vortex Rossby wave in Typhoon MANGKHUT (2018)

The mesoscale WRF model is used to simulate Typhoon MANGKHUT (2018) with high spatial resolution, and the fine dynamic structure and rainband characteristics of the typhoon are analyzed on this basis. The results show the dynamic configuration of low-level radial inflow and high-level radial outflow exists at the eye wall of Typhoon MANGKHUT, and there are high-value area of tangential wind speed and vertical ascending area near the eye wall, which incline outward with the height. The radar echo is strong and the convective system is deep near the eye wall. The disturbance field of vortex Rossby wave is obtained by scale separation method and the characteristics of vortex Rossby wave in the typhoon are analyzed. It is found wave 1 and wave 2 propagate in both tangential and radial directions, the amplitude of wave 2 is significantly smaller than that of wave 1, and the high-value area of positive vorticity disturbance of wave 1 and wave 2 basically covers the area of strong radar echo accompanied with strong convections; in the vertical direction, when the vorticity disturbance of the precipitation area is positive in the high level and negative in the low level and the divergence disturbance is vertically in the similar configuration, the convective systems will be strengthened, which is favorable for the enhancement of precipitation. Thus it can be seen that the dynamic configuration of high-level divergence and low-level convergence of the disturbance of wave 1 and wave 2 can promote the development of convective systems and has certain effect on the intensity and distribution of typhoon precipitation.