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

The relationship between tropical cyclones developing in the Northwest Pacific and El Nino is analysed and the triggering mechanism of the near-equatorial cyclones on El Nino is proposed. It is pointed out that the near-equatorial tropical cyclones developing equatorward of 10°N 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 Nino. The beginning period of El Nino ranges from January to May. The number of near-equatorial cyclones developing in this period determines whether El Nino can be generated or not. The persistence period is from June to September. El Nino can not continue developing unless there are adequate near-equatorial cyclones. If there are not, the developed El Nino will be broken down. The period from October to December is called the developing period. During this period El Nino may approach its culmination only when adequat