Oceanography Chapter 8 Vocab

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air mass
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A large mass of air with nearly uniform temperature, humidity, and density throughout.
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atmosphere
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The envelope of gases that surround a planet and are held to it by the planet’s gravitational attraction.
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atmospheric circulation cell
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Large circuit of air driven by uneven solar heating and the Coriolis effect. Three circulation cells form in each hemisphere.
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Bjerknes, Vilhelm (1862-1951)
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Pioneering Norwegian physicist and discoverer of the nature and formation of extratropical cyclones, which cause most mid-latitude weather.
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climate
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The long-term average of weather in an area.
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convection current
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A single closed-flow circuit of rising warm material and falling cool material.
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Coriolis effect
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The apparent deflection of a moving object from its initial course when its speed and direction are measured in reference to the surface of the rotating Earth. The object is deflected to the right of its anticipated course in the Northern Hemisphere and to the left in the Southern Hemisphere. The deflection occurs for any horizontal movement of objects with mass and has no effect at the equator.
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Coriolis, Gaspard-Gustave de (1792-1843)
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The French scientist who in 1835 worked out the mathematics of the motion of bodies on a rotating surface.
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cyclone
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A weather system with a low-pressure area in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Not to be confused with a tornado, a much smaller weather phenomenon associated with severe thunderstorms.
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doldrums
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The zone of rising air near the equator known for sultry air and variable breezes.
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equator
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0° latitude, an imaginary line equidistant from the geographical poles. The irregular imaginary line of thermal equilibrium between hemispheres. It is situated about 5° north of the geographical equator, and its position changes with the seasons, moving slightly north in northern summer. Also called the thermal equator.
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extratropical cyclone
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A low-pressure, mid-latitude weather system characterized by converging winds and ascending air rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. An extratropical cyclone forms at the front between the polar and Ferrel cells.
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Ferrel cell
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The middle atmospheric circulation cell in each hemisphere. Air in these cells rises at 60° latitude and falls at 30° latitude.
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front
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The boundary between two air masses of different density. The density difference can be caused by differences in temperature and/or humidity.
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frontal storm
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Precipitation and wind caused by the meeting of two air masses, associated with an extratropical cyclone. Generally, one air mass will slide over or under the other, and the resulting expansion of air will cause cooling and consequently, rain or snow.
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geographical equator
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0° latitude, an imaginary line equidistant from the geographical poles.
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Hadley, George (1685-1768)
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A London lawyer and philosopher who worked out the overall scheme of wind circulation in an effort to explain the trade winds.
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heat budget
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An expression of the total solar energy received on Earth during some period of time and the total heat lost from Earth by reflection and radiation into space through the same period.
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horse latitudes
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Zones of erratic horizontal surface air circulation near 30°N and 30°S latitudes. Over land, dry air falling from high altitudes produces deserts at these latitudes (e.g., the Sahara).
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hurricane
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A large tropical cyclone in the North Atlantic or eastern Pacific, whose winds exceed 118 kilometers (74 miles) per hour.
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intertropical convergence zone (ITCZ)
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The equatorial area at which the trade winds converge. The ITCZ usually lies at or near the meteorological equator; also called the doldrums.
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land breeze
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Movement of air offshore as marine air heats and rises.
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meteorological equator
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The irregular imaginary line of thermal equilibrium between hemispheres. It is situated about 5° north of the geographical equator, and its position changes with the seasons, moving slightly north in northern summer. Also called the thermal equator.
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monsoon
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A pattern of wind circulation that changes with the season. Also, the rainy season in areas with monsoon wind patterns.
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nor’easter (northeaster)
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Any energetic extratropical cyclone that sweeps the eastern seaboard of North America in winter.
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polar cell
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The atmospheric circulation cell centered over each pole.
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polar front
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Boundary between the polar cell and the Ferrel cell in each hemisphere.
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precipitation
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Liquid or solid water that falls from the air and reaches the surface as rain, hail, or snowfall.
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sea breeze
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Onshore movement of air as inland air heats and rises.
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storm
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Local or regional atmospheric disturbance characterized by strong winds often accompanied by precipitation.
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storm surge
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An unusual rise in sea level as a result of the low atmospheric pressure and strong winds associated with a tropical cyclone. Onrushing seawater precedes landfall of the tropical cyclone and causes most of the damage to life and property.
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thermal equator
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The irregular imaginary line of thermal equilibrium between hemispheres. It is situated about 5° north of the geographical equator, and its position changes with the seasons, moving slightly north in northern summer. See meteorological equator.
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thermal equilibrium
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The condition in which the total heat coming into a system (such as a planet) is balanced by the total heat leaving the system.
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tornado
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Localized, narrow, violent funnel of fast-spinning wind, usually generated when two air masses collide; not to be confused with a cyclone. (The tornado’s oceanic equivalent is a waterspout.)
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trade winds
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Surface winds within the Hadley cells, centered at about 15° latitude, that approach from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere.
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tropical cyclone
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A weather system of low atmospheric pressure around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. It originates in the tropics within a single air mass, but may move into temperate waters if the water temperature is high enough to sustain it. Small tropical cyclones are called tropical depressions, larger ones tropical storms, and great ones hurricanes, typhoons, or willi-willis, depending on location.
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tropics
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The area between the Tropic of Cancer and the Tropic of Capricorn.
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water vapor
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The gaseous, invisible form of water.
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weather
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The state of the atmosphere at a specific place and time.
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westerlies
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Surface winds within the Ferrel cells, centered around 45° latitude, that approach from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.
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wind
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The mass movement of air.

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