The Bjerknes hypothesis: More information at http://physicsweb.org/articles/world/11/8/8/1/world-11-8-7-4
Kelvin waves - are special gravity waves that propagate eastward with a speed of approximately 2-3 ms-1 in the ocean and have their maximum amplitude at the equator.
The delayed oscillator mechanism: get more information at: http://iri.columbia.edu/climate/ENSO/theory/waves.html
La NiNiñoa - means "Infant Girl" in Spanish and is so named because in many ways it is the opposite of El Niño. La NiNiñoa is characterized by large scale cooling of the tropical Pacific Ocean and often begins during the summer at irregular intervals of between about 2 and 7 years and lasting for 1 to 3 years
Monsoon - a name for seasonal winds, first applied to the winds over the Arabian Sea that blow for six months from the northeast and for six months from the southwest. The term has been extended to similar winds in other parts of the world, they are associated with very heavy rainfall. The North American monsoon occurs in late summer and affects Arizona, New Mexico, Utah and Colorado.
Source: http://www.free-definition.com/Monsoon.html; http://eobglossary.gsfc.nasa.gov/Library/glossary.php3?xref=monsoon
Rossby waves, which are driven by the variation of the Coriolis force with latitude, propagate westward at about 0.6-0.8 ms-1 near the equator. The oceanic Kelvin and Rossby waves carry energy and momentum received from the wind stress at the ocean surface. They also provide the oceanic "memory" that is so important to year-to-year variability and ENSO."
More information at http://www.soc.soton.ac.uk/JRD/SAT/Rossby/Rossbyintro.html The delayed oscillator mechanism: get more information at: http://iri.columbia.edu/climate/ENSO/theory/waves.html
The Southern Oscillation - is the periodic change (i.e., oscillation) of sea level pressure differences across the tropical Pacific that have been found to correlate with El Niño and La NiNiñoa events. First recognized by British scientist Sir Gilbert Walker in the 1920s who observed pressure differences between Darwin, Australia and Tahiti
The Southern Oscillation Index - (SOI) is the difference between the seasonally normalized sea level pressures of Darwin, Australia and Tahiti. A negative SOI (also called "low index") usually relates to a weakening of the Trade Winds and a resulting warm event. Conversely a positive SOI ("high index") usually relates to an increase in the Trades and a resulting cool event. [Table, Plot]
Teleconnections - A statistical relationship between conditions in one part of the world affecting the weather in a different part of the world. For example, there appears to be a teleconnection between the ENSO events and rainfall in California.
Thermocline - is the boundary layer between the warmer well-mixed surface water and colder deep ocean water. The depth of the thermocline is another indicator of an El Niño events when it deepens in the eastern Pacific. [Normal, El Niño, & La NiNiñoa examples]
Trade Winds - (also Trades or Tropical Easterlies) are the steady winds resulting from the circulation of air from the Subtropical High pressure regions toward the Equator and deflected to the west by the Coriolis Force. The convergence of these winds along the Equator is the Intertropical Convergence Zone (ITCZ). Because of the dependability of these winds they were used by sailing ships of the 17th and 18th centuries to establish "trade" with the New World. [Image of Trade Winds]
Upwelling - the upward motion of sub-surface water toward the surface of the ocean which is often a source of cold, nutrient-rich water. Significant upwelling occurs along the equator under the influence of persistent trade winds and also along coastlines.