Dynamics of El Niño Southern Oscillation

Abstract The hazards associated with El Niño Southern Oscillation (ENSO) are documented in the literature. They include but are not limited to droughts, floods, extreme temperatures, and tropical cyclone count cycles. It appears that during ENSO warming phases, the number of typhoons increases and the number of hurricanes decreases. The opposite occurs during cold phases. The present ENSO understanding assumes that the oscillation is self driven indefinitely, which is thermodynamically unfeasible. Energy supply is required. Furthermore, features of the observed Oceanic Niño Index have remained uncaptured by ENSO models, and long-term prediction of El Niño has remained a challenge. This work reveals that the observed uneven surface warming between the hemispheres induces heat cycles in the hydrosphere, the outcome of which is El Niño events. During an event, tropical winds are practically arrested, and wind thrust and momentum fluxes produce potential energy cycles of the tropical air mass. Fluctuation of the potential energy exchanges heat with sea water in El Niño region and warm and cold episodes of ENSO manifest. Accordingly, the theoretical equation of the Oceanic NiñoIndex is derived. It is compared with observations and an agreement appears to exist. The equation is then used to calculate and project the index between 2015 and 2024. Because the uneven warming between the hemispheres is increasing, the frequency of El Niño events is expected to increase.