El Niño/Southern Oscillation (ENSO) Definitions

Anomalies: Variations from an average or other statistical reference value.

Bimodal: Having two peaks (or modes).

Buoyant: As the air is heated it expands, becoming less dense than the air above it.

Convection: The transfer of energy by moving the heated molecule from one place to another – also the rising of heated air which forms cumuliform clouds and results in precipitation.

El Niño: Literally, El Niño translates to "The Boy Child" and is a reference to Jesus as a baby.

Holocene: The current geological epoch, beginning about 10,000 years before the present.

Infrared: Wavelength of radiation longer than visible light and associated with the "heat" given off by a body.

Moche: A pre-Colombian civilization in northern Peru that existed from about 100 to 800 A.D.

Paleoclimate Proxy Data: Climate information from before the invention of atmospheric monitoring instruments. This information is derived from known chemical and bioliogical indicators in layers of glacial ice, corals, sea floor sediments, tree rings, etc.

pre-Colombian: Referring to South and Central America in the period of time before European influence.

Pressure Gradient: A change in air pressure over a distance. The stronger the gradient, the faster the air will flow from the high pressure to low.

Sea Level Barometric Pressure: The force exerted by the atmosphere at sea level (zero meters elevation) as measured by a barometer.

Standardized: Adjusted so values from samples with different properties (e.g., months) can be compared to each other

Thermal Expansion: Heating an uncontained fluid or gas results in an increase in its volume as it attempts to maintain a constant pressure. In the ocean, since only the surface is unbounded, the expansion increases the sea level.


Thermocline: A zone beneath the ocean surface at which the surface water transitions to deep water, and a marked decrease in water temperature occurs. In both the surface (or mixed) layer and in the deep water, temperature is relatively constant with depth. Within the thermocline, water temperature quickly decreases from surface water temperature to deep water temperature.

Trade Winds: Winds in the tropics generally flow in an east to west direction (easterlies). So called because their consistency facilitated transoceanic sailing and commerce.