Ash Oro @ashoro.co.uk · 21/08/20262/ A quick primer first. ENSO is the El Niño–Southern Oscillation. El Niño is the ocean part. The Southern Oscillation is the atmospheric part. Essentially, the tropical Pacific Ocean and the atmosphere above it operate as a coupled system. 180
Ash Oro @ashoro.co.uk · 21/08/20263/ Normally, easterly trade winds push warm surface water westwards towards Indonesia. Cold water then rises off South America to replace the water moving away. That gives us a fairly well-understood pattern of sea temperatures, pressure, rainfall and winds. 180
Ash Oro @ashoro.co.uk · 21/08/20264/16 During El Niño, that system changes. The pressure difference across the Pacific weakens. The trade winds weaken with it. Warm water that would normally remain concentrated towards the western Pacific spreads eastwards. And the atmosphere responds. 190
