Effects of westerly wind bursts on El Nino: A new perspective

Daily observations from 1971 to 2010 reveal that every El Nino during this period was accompanied by congregated westerly wind bursts, suggesting a close relationship of these bursts with both cold tongue and warm pool El Nino events. With the addition of burst-like multiplicative noise to an intermediate ocean-atmosphere coupled model, it is shown that westerly wind bursts, by generating eastward equatorial surface currents and downwelling Kelvin waves, could be responsible for the existence of the warm pool El Nino and for the irregularity and extremes of the cold tongue El Nino. Whether these bursts give rise to one type of El Nino or the other depends on the timing of their occurrence relative to the phase of the recharge-discharge cycle of the equatorial upper ocean heat content.