台风“珍珠”(2006)螺旋雨带发展机制的数值模拟研究

基于2 km分辨率的ARW-WRF数值模拟资料,讨论了台风"珍珠"(2006)螺旋雨带中对流单体及内雨带的发展机制。结果表明:模式很好地再现了台风的路径和强度。作为雨带中仅仅存在于眼壁外侧的内雨带,其传播机制与重力波、涡旋Rossby波及混合波没有联系,其可能发展机制仅与低层出流、水平风场和变形场有关。低层出流使得内雨带径向向外运动,而低层的水平风场和变形场使其形成螺旋结构。同时,就螺旋雨带中精细对流单体的发展而言,涡度收支方程定量分析表明,其主要通过两种方式获得垂直涡度:水平涡度倾斜为垂直涡度;上升运动拉伸垂直涡度。随着平流输送,对流单体在眼壁附近合并和汇聚。

Numerical simulation of development mechanism of Typhoon Chanchu(2006) spiral rainbelts

Based on the Advanced Research Weather Research and Forecast(ARW-WRF) model simulations with the grid size of 2 km,the development mechanism of the convective cells in spiral rainbands and the inner rainbands in super Typhoon Chanchu(2006) was examined.Results show that the WRF model can well reproduce the track and intensity of the typhoon.Development mechanism of inner rainbands that exist only on the lateral side of the eye wall is not related with the gravity waves,the vortex Rossby waves and the mixed Rossby-Gravity Waves,and it may be only associated with the low-level radial outflow,the horizontal wind field and the deformation wind field.The convective cells of inner rainbands are advected radially outward by the low-level radial outflows and deformed into spiral shapes by the low-level horizontal and deformation wind fields.In terms of the development mechanism of fine convective cells in the spiral rainbands,they acquire vertical vorticity through the tilting of horizontal vorticity and the stretching of vertical vorticity based on the quantitative analysis of vorticity budget equation.With advection transport,the convective cells in different spiral rainbands are merged and converged near the eye wall.