Predicting ENSO
El Nino/Southern Oscillation (ENSO) is a climate phenomenon that is due to coupling between the atmosphere and ocean in the tropical Pacific. Important for the evolution of the atmosphere is the distribution of the Sea Surface Temperature (SST) that creates near surface
pressure gradients in the atmosphere (via atmosphere-ocean heat exchange, hydrostatic balance, and the
ideal gas law) and hence
drives the winds. Important for the ocean is the
surface wind stress, which drives ocean currents and upwelling (especially along the equator) and hence affects strongly the SST.
The time scale of ENSO (interannual) results from a competition of processes with comparable time scales (6-10 months): the dynamical adjustment time of the upper ocean in the tropics to a
change in the wind stress; the time for the upper ocean and atmosphere to come to a thermodynamic equilibrium. The result is a interannual climate phenomenon that
occurs every 2-7 years, with an average time between peak events (eg., El Nino) of
about four years. ENSO
creates global scale climate changes via atmospheric teleconnections.
A forecast of the state of ENSO over the next year is an example of a
climate forecast. The forecast
accuracy will depend on the quality of the AGCM, the ocean model (often an ocean GCM), the representation of the energy and moisture transfer between the two media, and the quality of the initialization of the
ocean. (the state of the ocean at initialization time is a result of the integrated effects of the
wind forcing over the past few years). This is very different set of criteria from the criteria for a good weather forecast (cf, section 1).
http://www.atmos.washington.edu/~david/enso/ENSO_dyn_activity.doc
Notice that the ideal gas law (PV=nRT) is used as an integral part of explaining El Nino. The uneven heating of the earth by the sun causes pressure gradients to form which causes wind to blow (equalize pressure and redistributes heat). Winds blowing across a surface, be it land or water or ice, causes frictional heating of the surface and the air above and is call wind stress.
This articles starts by explaining the difference between weather and climate forecast. It progresses from there.
The IPCC climate computer model does not incorporate the ENSO model. It does not include the ideal gas law. In short, the IPCC computer model is seriously flawed as witnessed by its predictions versus reality.