Energy circulation associated with interannual waves in the tropical-subtropical Pacific

Abstract The present study has investigated interannual variations in the tropical-subtropical Pacific Ocean by applying Helmholtz decomposition to wave energy fluxes to indicate the direction of group velocity. The main source of energy is located in the central equatorial Pacific Ocean, while the anticyclonic and cyclonic circulation of wave energy appears in the western and eastern tropical Pacific Ocean, respectively. In the western basin, the anticyclonic circulation of wave energy is overridden at low and mid-latitude regions by the westward transfer of wave energy associated with the energy flux potential. Regional averages of the energy flux streamfunction and energy-flux potential associated with El Niño and La Niña events are similar to each other and show a quadratic dependence on the observed Niño-3 index. For example, the regional average of the energy-flux potential associated with the wind input in the central Pacific Ocean may be regressed as 0.72 ∆T 2 + 0.31 (in giga watts), where ∆T is the sea surface temperature anomaly (in degrees Celsius) associated with the Niño-3 index. The symmetry between El Niño and La Niña events is owing to the fact that the wave energy quantities do not differentiate between upwelling and downwelling (Kelvin) waves.