Glossary of ENSO Terms
- anomaly
- The difference between the value of a variable (for example
temperature) at a given location and its long term average at that
location.
- circulation
- The flow or motion of a fluid.
- climatology
- A quantitative description of climate showing the
characteristic values of climate variables over a region. Climate
refers to the statistical collection of weather conditions over a
specified period of time. Note that the climate taken over
different periods of time (30 years, 1000 years) may be
different.
- convection
- Mass motions in a field resulting in transport and mixing of
the field. More specifically, it refers to motion associated with a
rising current of air.
- coupled model (or coupled
atmosphere-ocean model).
- In the context of climate modeling this usually refers to a
numerical model which simulates both atmospheric and oceanic
motions and temperatures and which takes into account the effects
of each component on the other.
- cumulonimbus
- A cloud type that is dense and vertically developed and is
associated with rain (particularly of a convective nature).
- composite
- An average that is done according to a specific criteria. For
example, one could composite the rainfall at a station for all
years where the temperature was much above average.
- jet stream
- Strong winds concentrated within a narrow zone in the
atmosphere. Often used in reference to the axis of maximum
mid-latitude westerlies located in the high troposphere.
- monsoons
- Seasonal winds. They are caused primarily by the greater annual
variation in air temperature over large land surfaces compared to
ocean surfaces though other factors like land-relief are
important.
- stationary waves
- Waves (flow patterns with periodicity in time and/or space)
that are fixed relative to Earth.
- storm track
- The path followed by the center of a low (of atmospheric
pressure). In many cases, multiple storms follow the same storm
track.
- teleconnection
- A strong statistical relationship between weather in different
parts of the globe. For example, there appears to be a
teleconnection between the tropics and North America during El
Niño.
- thermocline
- As one descends from the surface of the ocean the temperature
remains nearly the same as it was at the surface. Soon, however,
one encounters a zone in which temperature starts decreasing
rapidly with depth. This zone is called the thermocline. The
thermocline is important because it can support large scale waves
which play a major role in ENSO. In studying the tropical Pacific
Ocean, the depth of 20C water ("the 20C isotherm") is often used as
a proxy for the depth of the thermocline. Along the equator, the
20C isotherm is typically located at about 50m depth in the eastern
pacific, sloping downwards to about 150 m in the western
Pacific.
- upwelling
- In ocean dynamics, the upward motion of sub-surface water
toward the surface of the ocean. This is often a source of cold,
nutrient-rich water. Strong upwelling occurs along the equator
where easterly winids are present. Upwelling also can occur along
coastlines, and is important to fisheries in California and
Peru.
*definitions adapted from the "Glossary of Meteorology" 1959.