Effect of atmospheric action center in low-frequency teleconnection mechanism: an explicit analytic study

In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean stream field as the basic stream field, an approximate analytical formula for the period of atmospheric low-frequency oscillation (LFO) and the group velocity is deduced from a barotropic and non-divergent linearized vorticity equation. All the action centers of atmosphere are found to be the oscillators of low frequency. The LFO propagates southward across the streamlines in the wind field with a southward component or propagates northward across the streamlines in the wind field with northward component instead of along a great circle. The switch of the propagation direction takes place near the top of ridge or the bottom of trough. The angle between the wave rays and the zonal direction can be determined. Project supported by the National Natural Science Foundation of China (Grant No. 49175241).