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Unformatted text preview: The atmosphere in motion The Air pressure Air Air Air pressure: pressure exerted by the air above above Average air pressure at sea level: 14.7 Average pounds per square inch pounds Meteorologists measure pressure in Meteorologists millibars (1 atmosphere = 1013.2 millibars) millibars Measuring air pressure Measuring Air pressure is measured using a barometer In a barometer, when air pressure increases, the In mercury in the tube rises mercury Standard atmospheric pressure is equal to 29.92 inches Standard of mercury of Sometimes, an aneroid barometer is used This barometer is connected to a barograph Wind Wind Wind Wind is the result of horizontal differences in air pressure in Air flows from areas of higher pressure to Air areas of lower pressure areas Solar radiation is the ultimate energy Solar source for most wind source Pressure Pressure differences create wind, the greater the pressure differences, the greater the wind speed greater How wind is measured How Wind is measured by one of two devices: 1) wind vane: Used to measure wind direction direction 2) cup anemometer: used in measuring wind speed wind Factors affecting wind Factors Pressure gradient force Coriolis effect friction Pressure gradient force Pressure This This is the amount of pressure change over a distance over Pressure data on weather maps is shown Pressure using isobars using Isobars are lines that connect places of Isobars equal pressure equal Closely Closely spaced isobars indicates high winds, whereas widely spaced isobars indicates light winds indicates Coriolis effect Coriolis This This is the deflective force of Earth’s deflective rotation on all free-moving objects rotation All free-moving objects (including wind) All are deflected to the right of their path of motion in the Northern Hemisphere and to the left in the Southern Hemisphere the Coriolis effect (cont.) Coriolis Shift Shift in wind direction is due to the Coriolis effect effect Friction Friction Friction acts to slow air movement and alters wind direction alters Friction lowers wind speed, and reduces Friction the Coriolis effect the Cyclones and anticyclones Cyclones Cyclone: Center of low pressure Anticyclone: center of high pressure In a cyclone, pressure decreases from the In outer isobars towards the center outer In In an anticyclone, values of isobars increases from the outer isobars to the center center Highs and Lows Highs Winds Winds move from higher pressures to lower pressures and are deflected from left to the right by Earth’s rotation left In In the Northern hemisphere, winds blow inward and counterclockwise around a low pressure system and outward and clockwise around a high pressure system clockwise High and Lows (cont.) High Low Low pressure systems bring cloudiness and precipitation and High pressure systems usually bring in High clear skies and fair weather clear ...
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This note was uploaded on 12/25/2010 for the course ESC 1000 taught by Professor Faculty during the Fall '10 term at FAU.
- Fall '10