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A study on mechanics of polar lows developed by cold vortex aloft using idealized numerical experiments and potential vorticity analysis

利用理想化数值实验和位涡分析研究高空冷涡产生的极地低气压的力学

基本信息

批准号：
22540446
负责人：
IGA Keita
金额：
$ 2.33万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2010
资助国家：
日本
起止时间：
2010 至 2012
项目状态：
已结题

项目摘要

We investigated the mechanism of the development of polar lows excited by cold vortex aloft, through numerical experiments using meso-scale atmosphere model under idealized simple conditions. When the level of the cold vortex is low and the atmosphere is weakly stratified, the dynamic effect that the vortex aloft directly excites the surface disturbance is dominant. On the other hand, when the cold vortex is situated high and the stratification is strong, the thermal effect that the stratification of the lower-level atmosphere weakened by the cold air aloft enhances the convective motions becomes evident. As for the dynamical effect, the mechanism that the surface vortex is stretched by the upward motion driven by the advection of potential vorticity aloft is more significant than the mechanism that the advection at the sea-surface level interacts with the potential vorticity gradient.

通过中尺度大气模式在理想简单条件下的数值试验，研究了高空冷涡激发下极地低气压的发展机制。当冷涡水平较低，大气分层较弱时，高空涡旋直接激发地面扰动的动力作用占主导地位。另一方面，当冷涡处于高位且分层强时，低层大气的分层被高空冷空气削弱而增强对流运动的热效应就变得明显。在动力效应方面，由高空位涡平流驱动的上升运动对地面涡的拉伸机制比海面平流与位涡梯度的相互作用机制更为显著。