ON THE MECHANISM OF TELECONNECTIONS BETWEEN EL NINO AND EAST ASIAN ATMOSPHERIC CIRCULATION

Based on the linear planetary wave theory and observed data,the teleconnections between El Nino and atmospheric circulation in the Northern Hemisphere(NH) are studied.It is shown that the zonal group velocity for stationary Rossby waves in the atmosphere is always positive.Thus,the energy of these disturbances can not propagate westward.In certain conditions,however,the westward propagation of nonstationary waves is possible.Going further into this question,we prove that the low-frequency disturbances over the eastern equatorial Pacific,which are closely related to the large-scale air-sea interaction in low-latitudes,can influence the extratropical atmospheric circulation in the NH along two typical energy paths;i.e.,the waves with wavenumber one(n=1) propagate through the western North Pacific into East Asia and form the "East Asian Path",which plays an important part in the teleconnections between El Nino and atmospheric anomalies over East Asia,besides,the waves with n≥2 propagate along the "PNA Path" into the middle and eastern North Pacific as well as North America,leading to the relevant atmospheric anomalies to be excited over there.