climatology and meteorology


a cold wind blowing down an incline; a kind of katabatic wind.

Bermuda high

the semipermanent subtropical high over the North Atlantic Ocean, especially when it is located over the western part of the ocean; the same high over the eastern part of the Atlantic is called the Azores high; on mean charts of sea level pressure, this high is one of the primary centers of action in northern latitudes.

arctic circle

a line of latitude at approximately 66 degrees 33 minutes N (66°33’ N) that marks the border of the Arctic, the northernmost region of Earth. Along this line, the sun does not set on the day of the summer solstice, and does not rise on the day of the winter solstice.


an instrument for measuring atmospheric pressure; two types of barometers are commonly used in meteorology: the mercury barometer and the aneroid barometer.


a barometer that records barometric pressure over time (days or weeks).

average value

arithmetic mean (m) of a number (n) of values (x1, x2, ... xn), defined by the equation: m = sxi/n; annual average value is calculated from 12 monthly means; daily average (or mean) value is calculated from 24 hourly readings of a meteorological element, or often from the average of the daily maximum and minimum values (for example, of temperature); monthly average is usually calculated as the average of the daily average values.


luminous phenomena, in the form of arcs, bands, draperies, or curtains in the high atmosphere over high latitudes; auroras are related to magnetic storms and the influx of charged particles from the sun, the phenomena are called aurora borealis in the northern hemisphere and aurora australis in the southern hemisphere.

atmospheric radiation

longwave (infrared) radiation emitted by or being propagated through the atmosphere.

atmospheric pressure

pressure (force per unit area) exerted by the atmosphere on any surface by virtue of its weight; it is equivalent to the weight of a vertical column of air extending above a surface of unit area to the outer limit of the atmosphere.

atmospheric phenomenon

as commonly used in weather observing practice, an observable occurrence of particular physical significance within the atmosphere; from the viewpoint of weather observations, the atmospheric phenomena include all hydrometeors (precipitation types and fogs), blowing snow, thunderstorms, tornadoes, waterspouts, and others.


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