Influence of the basic flow in the Tropics on stationary planetary waves at middle and high latitudes during the Northern Hemisphere winter

The relationship between the quasi-stationary planetary waves forced by topography and the heat source in the Northern Hemisphere is investigated by means of a quasi-geostrophic, 34-level spherical model with Rayleigh friction, Newtonian cooling, and horizontal eddy thermal diffusivity. The computed results show that, when the basic flow in the tropical stratosphere is westerly, the amplitude of the quasi-stationary planetary wave for zonal wavenumber 2 at middle and high latitudes during the Northern Hemispheric winter is larger; when the basic flow in the tropical stratosphere is easterly, it is smaller. This is in agreement with the actual observed results. The computed results also show that the influence of the basic flow in the tropical troposphere on the quasi-stationary planetary waves is larger than that of the basic flow in the tropical stratosphere on the quasi-stationary planetary waves.