THE TRIGGERING EFFECT OF NEAR-EQUATORIAL CYCLONES ON EL NI?O

The relationship between tropical cyclones developing in the Northwest Pacific and El Ni?o is analysed and the triggering mechanism of the near-equatorial cyclones on El Ni?o is proposed. It is pointed out that the near-equalorial tropical cyclones developing equatorward of 10oN can intensify equatorial westerlies and produce Kelvin waves, which propagate to the South American Coasts in about 2-3 months, inducing SST to rise there. The near-equatoral cyclones play an essential role in El Ni?o. The beginning period of El Ni?o ranges from January to May. The number of near-equatorial cyclones developing in this period determines whether El Ni?o can be generated or not. The persistence period is from June to September. El Ni?o can not continue developing unless there are adequate near-equatorial cyclones. If there are not, the developed El Ni?o will be broken down. The period from October to December is called the developing period. During this period El Ni?o may approach its culmination only when adequate near-eqatorial cyclones have been developed east of 140oE, especially east of 160oE.