THE ROLE OF THE MERIDIONAL CIRCULATION IN STATIONARY WAVE PROPAGATION

In a general baroclinic atmosphere,when the basic state includes meridional circulation,the stationary waves might not only pass through the equatorial easterlies,but also strengthen significantly.The orographic forcing in the Northern Hemisphere mid-latitude might cause marked responses in the low latitude atmosphere.This suggests that the meridional circulation plays an important role in the connection of stationary responses in mid and low latitudes,and so does the heating forcing in the Northern Hemisphere mid-latitude.Forced by the heating forcing in the Northern Hemisphere midlatitude,the features similar to the Northern Hemisphere summer monsoon circulation can be obtained.It appears that the meridional circulation plays certain role in the formation of summer monsoon circulation.The heating anomaly forcing located at the eastern equatorial Pacific makes the stationary waves present PNA(Pacific-North America) pattern in the winter hemisphere,but it does not in the summer hemisphere.It suggests that the meridional circulation has a marked influence on the route of stationary wave propagation both in the winter and summer hemispheres.