Chapter_5_notes - Chapter 5 Winds and the Global...

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Unformatted text preview: Chapter 5 Winds and the Global Circulation System ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atmospheric Pressure • We live at the bottom of an ocean of air • Since this air has mass, it will exert pressure on the surface below it • The more air, the greater the pressure – thus, pressure decreases with altitude • Air is easily compressible – thus, its density decreases with altitude ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atmospheric Pressure • In meteorology, we measure atmospheric pressure using a unit of measure called the millibar (mb) • 1000 millibars = 1 bar • 1 bar is approximately equal to one atmospheric pressure • Hence, atmospheric pressure at sea level is 1013.25 millibars or 29.92 inches (?) • At sea level, air pressure may vary from about 980 mb to 1030 mb (about 5%) ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atmospheric Pressure • Atmospheric pressure is measured using an instrument called a barometer • An older type of barometer is called a mercurial barometer , which measures atmospheric pressure as an equivalent weight of a column of mercury • Hence, sea-level pressure also can be defined as 29.92 inches of mercury ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atmospheric Pressure • A more common type of barometer is the aneroid barometer • It uses the pressure exerted against a partial vacuum to measure air pressure ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ Atmospheric Pressure • Pressure Gradient – variation in atmospheric pressure from one place to another • In nature, anytime a gradient exists, there will be a force created that attempts to equalize the gradient • With pressure, we call this gradient the Pressure Gradient Force...
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This note was uploaded on 10/28/2009 for the course GEOG 101 taught by Professor Lavin during the Fall '08 term at University of Delaware.

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Chapter_5_notes - Chapter 5 Winds and the Global...

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