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.