The Influence of Structure of Upper-tropospheric Cold Vortex on Typhoon Motion
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摘要: 通过对不同水平和垂直结构的高层冷涡在台风移动中的作用的对比试验,发现高层冷涡的水平和垂直结构变化会影响台风的运动。对总涡度倾向分布和强度的比较分析,发现正压过程主导台风运动的方向,而斜压过程在某些情况下对台风移速有很大影响。通过各动力项对总涡度倾向贡献的讨论,发现涡度平流对总涡度倾向正中心的贡献主要来自引导气流对非对称涡度场的平流。散度场贡献主要来自行星涡度和非对称散度相关场。最后还得到预报性的结论:台风朝对流层上层的辐合中心或对流层中下层辐散中心方向移动。Abstract: The role of upper-tropospheric cold vortex with different horizontal and vertical structures in the process of typhoon movement is studied. It is found that the structural variation of aloft cold vortex will affect the typhoon motion. The analysis shows that barotropic processes dominate in direction of motion, but under some circumstances, baroclinic processes dominate in its speed. Furthermore, it is also shown that contribution of horizontal vorticity advection to the positive center of TVT (total vorticity tendency) comes from the advection of asymmetric vorticity with steering current, and contribution of divergence field to TVT is mainly from the correlation field between the planetary vorticity and asymmetric divergence. Finally, it is concluded that within the ranging affected by the cold vortex, typhoon will move to the regions of convergence center in the upper-troposphere or divergence center in the mid-and-lower troposphere. This conclusion is useful to forecasters
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Key words:
- Typhoon motion;
- Cold vortex;
- Total vorticity tendency
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