初始涡旋结构对热带气旋强度变化影响的数值研究

Numerical study of the influence of initial vortex structure on the intensification of tropical cyclones

本文利用中尺度WRF模式,通过构造3个位于不同高度上强度相同的初始涡旋暖心中心(分别称为Low试验、Mid试验和High试验),认识暖心垂直结构对热带气旋发展的影响。理想数值试验发现,在积分6h后在Low试验和Mid试验中最大风速半径开始收缩,眼墙内对流发展,高层暖心发展明显比High试验强,强度增加明显快于High试验,达到快速增强的标准。进一步诊断发现,暖心偏低的试验中初始CAPE值较大,低层风垂直切变较强,有利于眼墙内对流发展,非绝热加热在高层暖心形成过程中起重要作用,最大风速半径收缩比High试验快,热带气旋强度快速增加。本研究清楚表明,数值预报模式中构造初始涡旋的暖心高度对模拟热带气旋的强度发展有重要影响。

Although the vertical structure of tropical cyclone warm core is closely related to the change of intensity,there is no direct observation of the three-dimensional warm-core structure of tropical cyclone,and how to construct the initial vortex in numerical prediction models is still a research topic.To explore the effect of vertical structure of warm core on the development of tropical cyclone,the mesoscale WRF model was used to construct three warm cores of initial vortexes with same intensity but different height for the low test,middle test and high test,respectively.The simulation result shows that the maximum wind speed radius in the low and mid tests begins to contract after 6 h and the convection in the eye wall begin developing.And the intensity of the high warm core is obviously stronger than that of the high test.The increase in intensity in low and mid tests is also faster than that in the high test,and reaches the rapid intensification.The further diagnoses show that the initial CAPE value is higher and the low-level vertical wind shear is stronger in the low test,which is favorable for convection development in the eye wall.The diabatic heating plays an important role in the formation of the high-level warm core;the contraction rate of maximum wind speed radius is faster than that the high test,and the intensity of the tropical cyclone increases rapidly.This study clearly shows that the warm core height of the initial vortex in the numerical prediction model has a significant effect on the development of simulated tropical cyclone intensity.