Current research on El Niño
Much still remains uncertain. For example:
- Is the Walker cell really self-sustaining?
- What sets an ENSO off?
- What other things influence the system?
- Are all the effects described really effects or are some of them causes?
Recent computer models indicate that the reduced rainfall during La Niña allows the sun to heat the ocean, especially in the deep western Pacific warm pool. This heat allows the circulation to continue. During El Niño, however, heat is trans
ported from the tropics to higher latitudes by ocean currents and additional heat goes to the atmosphere, mainly through evaporation. Thus the tropical Pacific loses heat during El Niño and gains it during La Niña. It may be that the time ta
ken to 'recharge' the ocean with heat determines when the events start and stop? Perhaps. But various other causes are indicated by some models:
- Atmospheric changes over the South Pacific often preceed SO changes by one to three seasons
- Anomalous snowfall over Asia and the SE Asian monsoon
- Volcanic eruptions
- Wave disturbances that travel across the ocean may trigger it
- Random weather "noise"
These last two possibilities give a real example of the theoretical chaos "butterfly" effect.
Further problems arise because of the rise in average tropical temperature: it seems that the baseline against which El Niño events are measured may have to be reset. Advances in the theory and modelling of El Niño can be found here.
Yet another general account of El Niño has, at the bottom of the page, a list of current research references on the web.
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