On the circuit and propagation of El Niño/La Niña signals

Based on the T/P altimeter dataset between October 1992 and December 2000,the circuit of El Niño/La Niña signals are studied.(1) In El Niño cases,positive sealevel anomaly(SLA) signals propag ate eastward from equatorial west to east in the Pacific.After reaching the coastal area,the signals go to polar directions along the eastern boundary and continuously generate westward propag ating Rossby waves.In the period of El Niño,the fact that the signal of the Rossby waves is the strongest near 10°N suggests that an signal circuit bounded by the equator and 10°N exists.The other El Niño signal circuit bounded by the equator and 10°S also exists,however relatively weak compared with its northern counterpart.Westward La Niña signals mainly are located in the channels centered 5°N and 7°S respectively.Westw ard seasonal signals mainly are located in the three channels centered at 6°N,10°N and 8°S respectively.(2) Two kinds of signals,fast and slow,transport El Niño information from East to West Pacific at the same latitude.The phase speed of the slow one with wavelength of 700~800 km is consistent with that of Rossby wave.The basin scale signals propagate so fast that it should be the oceanic response to atmospheric anomaly.