Chapter4 - Chapter 4 Atmospheric and Oceanic Circulation...

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Chapter 4 Atmospheric and Oceanic Circulation Atmospheric Circulation Large-scale air circulation transports heat Sensible heat and latent heat in water vapor Atmospheric circulation must transport heat from regions of surplus (Equator) to regions of deficit (poles) Atmospheric circulation important transfer of energy (heat) and mass Imbalance between energy surpluses at Equator and deficits at poles partly resolved Atmospheric circulation has enormous impact on Earth’s weather patterns and ocean currents Human-induced pollution also spread Air Pressure Air is composed of gases Motion, size, number cause pressure to be exerted on all surfaces in contact with air Pressure would crush us except that it also exists inside us and pushes back Air pressure measured by a barometer (mercury or aneroid) For every 900 ft. rise in elevation, pressure diminished by 1/30 th of itself Lowered pressure decreases amount of oxygen entering the blood through the lungs At high elevations, atmospheric pressure less, boiling point lower 10,000 ft. boiling point is 194 o F Water takes longer to boil 1013.2 mb = normal air pressure at sea level Up to 1040mb = “high” Down to 982mb = “low” Wind Horizontal motion of air across Earth’s surface (Vertical updrafts and downdrafts due to turbulence) Wind is caused by differences in air pressure (pressure gradient) Two main properties are speed and direction Speed measured with anemometer Direction measured with wind vane Speed expressed as kilometers per hour (kmph), miles per hour (mph), meters per second (mps) or knots 1 knot = 1.15mph (nautical mile per hour) Driving Forces Within the Atmosphere
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Gravity Pressure Gradient Force Coriolis Force Friction Force Gravity Earth’s gravitational force almost uniform Equal compression of atmosphere near the ground, worldwide Density of air decreases with altitude Pressure Gradient High and low pressure areas exist primarily due to unequal heating of Earth’s surface Pressure gradient = difference in atmospheric pressure between area of higher pressure and area of lower pressure Air moves from areas of higher pressure to areas of lower pressure Æ Similar to concept of water flowing downhill The steeper the gradient, the stronger the wind Air pressure shown on maps as isobars Lines connecting points of equal pressure (like contour lines on topographic map) Distance between isobars indicates degree of pressure difference Closer isobars denote steeper pressure gradients High pressure air usually sinks (descends) and diverges Low pressure air usually rises (ascends) and converges
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This note was uploaded on 04/20/2008 for the course GEOS 200 taught by Professor Hanchette during the Spring '08 term at University of Louisville.

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Chapter4 - Chapter 4 Atmospheric and Oceanic Circulation...

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