北半球西风带准周期性转换的理论分析——初步探讨北极与中纬度及副热带能量相互输送的机制

本文运用准地转模式，通过等值投影方法，将等值线转换为向量场结构，探讨西风带高低指数周期性转换的机制，结果表明:（1）仅有位能转化所引起的水平涡动输送，可能产生大振幅的行星波，但不会产生西风带的断裂；（2）在波流相互作用下，平均纬向风速与基波波幅满足分岔条件时，会出现西风带断裂现象，即当满足这个分岔条件时，更有利于北极与中纬度及副热带能量的相互输送。如北极冷空气的跨纬度输送会导致东亚极端冷事件的发生；同时，也能维持西风带的高低指数循环。

Theoretical Analysis of the Quasi-periodic Conversion of Westerlies in the Northern Hemisphere-Preliminary Discussion on the Mechanism for Energy Transport between the Arctic and the Mid-latitudes and the Subtropics

In this paper, a quasi-geostrophic model is used to convert contour lines into vector field structure by the equivalent projection. The results show that:(1) Horizontal vortex transmission caused by potential energy conversion may generate planetary waves with large amplitude, but it will not break the westerlies; (2) the fracture of the westerlies will occur when the average zonal wind velocity and wave amplitude meet the bifurcation condition under the wave flow interaction. Namely, it is more conducive to the mutual transmission of energy between the Arctic and the middle latitudes and the subtropics when this bifurcation condition is satisfied. For example, the translatitudinal transportation of Arctic cold air leads to the extreme cold events over East Asia. At the same time, it can maintain the high and low index cycle of the westerlies.