The difference between the value of a variable (for example
temperature) at a given location and its long term average at that
The flow or motion of a fluid.
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
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
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.
A cloud type that is dense and vertically developed and is
associated with rain (particularly of a convective nature).
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.
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.
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
Waves (flow patterns with periodicity in time and/or space)
that are fixed relative to Earth.
The path followed by the center of a low (of atmospheric
pressure). In many cases, multiple storms follow the same storm
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
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
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
*definitions adapted from the "Glossary of Meteorology" 1959.