Participation of off-equatorial wave energy for the Atlantic Niño events identified by wave energy flux in case studies

In the tropical Atlantic Ocean, extreme climate events with anomalous sea surface temperature, current, and precipitations are often referred to as the Atlantic Niño. It has many similarities with the EI Niño including the analogous mechanism that winds above the western equatorial ocean will excite oceanic waves to amply the temperature anomaly in the east. However, the Atlantic Niño presents more diversity in its intensity and occurrence time, especially in recent years, eg. 2019 and 2021, in which the classic theory becomes insufficient to explain. This study focuses on ocean responses to atmospheric forcing, manipulating the wind forcing in both equatorial and off-equatorial regions to excite linear ocean models for three types of events that occurred in 1999, 2019, and 2021 respectively. This study has found those extraordinary Atlantic Niños may owe to the wind in the off-equatorial region, where the winds can also excite oceanic waves that transfer energy to the western boundary and reflect back to the equatorial Atlantic. The interaction between the energy from the equatorial and the off-equatorial region makes the event less predictable. The participation of off-equatorial wave energy leads to the diversity of the Atlantic Niños. Hence, for the Atlantic Niño forecast,  more concerns about ocean dynamics to cover a wider latitude range should be required.