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23 Cards in this Set
- Front
- Back
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eddy
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A circular movement of water usually formed where currents pass obstructions, or between two adjacent currents flowing in opposite directions, or along the edge of a permanent current.
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doldrums
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The zone of rising air near the equator known for sultry air and variable breezes. Also known as the intertropical convergence zone. See also intertropical convergence zone (ITCZ).
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westerlies
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Surface winds within the Ferrel cells, centered around 45° latitude, which approach from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.
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countercurrent
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A surface current is flowing in the opposite direction from an adjacent surface current.
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Hadley cell
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The atmospheric circulation cell nearest the equator in each hemisphere. Air in these cells rises near the equator because of strong solar heating there and falls because of cooling at about 30° latitude. See also trade winds.
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Ekman spiral
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A theoretical model of the effect on water of wind blowing over the ocean. Because of the Coriolis effect, the surface layer is expected to drift at an angle of 45° to the right of the wind in the Northern Hemisphere and 45° to the left in the Southern Hemisphere. Water at successively lower layers drifts progressively to the right (N), or left (S), though not as swiftly as the surface flow.
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trade winds
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Surface winds within the Hadley cells, centered at about 15° latitude, which approach from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere.
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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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sea breeze
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Onshore movement of air as inland air heats and rises.
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convergence zone
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The line along which waters of different density converge. Convergence zones form the boundaries of tropical, subtropical, temperate, and polar areas.
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El Nino
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A southward-flowing nutrient-poor current of warm water off the coast of western South America, caused by a breakdown of trade wind circulation.
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land breeze
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Movement of air offshore as marine air heats and rises.
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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 (for example, the Sahara).
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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. See also Hadley cell; Ferrel cell; polar cell.
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upwelling
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Circulation pattern in which deep, cold, usually nutrient-laden water moves toward the surface. Upwelling can be caused by winds blowing parallel to shore or offshore.
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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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La Nina
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An event during which normal tropical Pacific atmospheric and oceanic circulation strengthens, and the surface temperature of the eastern South Pacific drops below average values. Usually occurs at the end of an ENSO event. See ENSO.
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gyre
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Circuit of mid-latitude currents around the periphery of an ocean basin. Most oceanographers recognize five gyres plus the West Wind Drift.
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Ferrell 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. See also westerlies.
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downwelling
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Circulation pattern in which surface water moves vertically downward.
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gulf stream
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The strong western boundary current of the North Atlantic, off the east coast of the United States.
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Langmuir circulation
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Winds that blow steadily across the ocean, and the small waves that such winds generate, can induce long sets of counter-rotating cells in the surface water.
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net water transport
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Net water transport, the sum of layer movement due to the Ekman spiral. Theoretical Ekman transport in the Northern Hemisphere is 90° to the right of the wind direction.
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