Two different features of discharge of equatorial upper ocean heat content related to El Niño events

Abstract

Oceanic and atmospheric anomaly fields in the tropical Pacific are investigated to extract some characteristics from twelve El Niño events in the past 49 years. The results show that entire equatorial upper ocean heat content (Teq) is discharged after the mature phase of seven El Niño events (A‐type events), while Teq is not well discharged in other five events (B‐type events). Furthermore, A‐type events generally have larger amplitudes of tropical oceanic and atmospheric anomalies than B‐type events. In addition, the durations of A‐type events are longer than those of B‐type events. It is also found that A‐type events accompany large positive wind stress curl anomaly and resultant poleward Sverdrup transport in the tropical South Pacific after the mature phase of El Niño events, while B‐type events do not. This appearance of large positive wind stress anomaly should be one of the reasons why Teq is well discharged in A‐type events.