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air pressure
The force exerted by the weight of a column of air above a given point.
an instrument that measures atmospheric pressure
pressure gradient
the amount of pressure change occurring over a given distance
Coriolis effect
the apparent deflective force of Earths rotation on all free-moving objects, including the atmosphere and oceans: deflection is to the right of the Northern Hemisphere and to the left in the Southern Hemisphere
jet stream
swift high-altitude winds
a low-pressure center characterized by a counterclockwise flow of air in the Northern Hemisphere
a high-pressure center characterized by a clockwise flow of air in the Northern Hemisphere
trade winds
two belts of winds that blow almost constantly from easterly directions and are located on the north and south sides of all subtropical highs
the dominant west-to-east motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highs.
polar easterlies
in the global pattern of prevailing winds, winds that blow from the polar high should not be thought of as persistent winds, such as the trade winds.
an instrument used to determine wind speed.
prevailing wind
a wind that consistently blows from one direction more than from another.
el nino
the name given to the periodic warming of the ocean that occurs in the central and eastern Pacific; a major el nino episode can cause extreme weather in many parts in the world.
air mass
a large body of air that is characterized by similar temperatures and amounts of moisture at any given altitude.
the boundary between two adjoining air masses having contrasting characteristics.
cold front
a front along which a cold air mass thrusts beneath a warmer air mass.
warm front
a front along which a warm air mass overrides a retreating mass of cooler air.
stationary front
a situation in which the surface position of a front does not move; the flow on either side of such a boundary is nearly parallel to the position of the front.
occluded front
a front formed when a cold front overtakes a warm front; it marks the beginning of the end of a middle-latitude cyclone
a storm produced by a cumulonimbus cloud and always accompanied by lightning and thunder; it is of relatively short duration and usually accompanied by strong wind gusts, heavy rain, and sometimes hail.
a small, very intense cyclonic storm with exceedingly high winds, most often produced along cold fronts in conjunction with severe thunderstorms.
a tropical cyclonic storm having winds in excess of 119 kilometers per hour
eye wall
the doughnut-shaped area of intense cumulonimbus development and very strong winds that surrounds the eye of a hurricane
a zone of scattered clouds and calm averaging about 20 kilometers in diameter or the center of a hurricane
storm surge
the abnormal rise of the sea along a shore as a result of strong winds.