Test 2 notes - U Air Pressure and Wind 2/3/10 Basic...

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U Air Pressure and Wind 2/3/10 Basic definitions Average surface pressure= 1013 milibars ( mb) High pressure=atmosphere “heavy” ( >1013 mb) Low pressure= atmosphere “light” ( <10103 mb) Pressure gradient= a change in air pressure with horizontal distance o Steep gradient= big pressure change between two areas Strong winds, tightly packed isobar o Gradual gradient= Isobars spread out and weak winds o A to B about 2400 mi= P change = 18 mb Pressure gradient force ( PGF)= Pressure difference that causes the air to move form H –L Descending diverging= Air “piles up”, air descends and hits the surface and spreads out. HIGH PRESSURE Ascending converging= Vacuum created, rising air. LOW PRESSURE o Tornados is example of LOWEST pressure possible Wind= horizontal flow of air from H- L pressure Differential heating: sea breezes ( daytimes ) o Wind from ocean comes is as cold temperature ( high pressure) and then heats at the land becomes Higher temperature ( low pressure) as it rises- then it circulates back and the warm air cools and the cycle starts again. Differential heating: land breezes ( night) o Lower temperature ( higher pressure ) at land- cooler air is drawn offshore- heated air rises over warmer water then cycles back Differential heating: Monsoons ( circulation reversal)- giant land and sea breeze o Winter- cold air diverges away from land o Summer- warm air moves toward the land Energy imbalance Temperature DIFFERENCES—Pressure DIFFERENCES--- wind o What the temperature relative to surrounding areas o North America Winter—southern U.S kind of warm, North very cold HUGE temperature diff from north to south Greater T differences in winter—Greater PGF— Greater winds Summer- Not much difference from north to south – its all warm- less winds bc less T difference and less PGF Coriolis effect= apparent deflection in the path of a moving object due to the earths roataion. o Happens because: The earth is a sphere Rotational velocity varies The earth is rotating with latitude Objects are moving independent of the earth ( airplanes ) Merry go round- cant throw something to someone elsei
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Northern Hemisphere: Reflected To the right Southern hemisphere: Reflected to the left Coriolis STRENGHT on Latitude: maximum degree of deflection at poles, 0 at the equator Wind velocity: > deflection with faster wind Global Circulation 2/5/10 Surface winds o Affected by: Pressure Gradient Force Coriolis Effect Friction==slows wind down Friction will cause less coriolis deflection Northern Hemisphere winds in a HIGH PRESSURE= PGF have outward flow of air all wind resulting winds blows to the right of each ( outward and clockwise) Northern Hemisphere winds in a Low pressure= PGF merge in and the resulting winds go In to the right ( inner and counter- clockwise) – Tornadoes form in low pressure cells Surface winds- cyclonic circulation( circulation u have around low pressure)
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This note was uploaded on 06/05/2011 for the course GEOG 1111 taught by Professor Hopkins during the Spring '08 term at University of Georgia Athens.

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Test 2 notes - U Air Pressure and Wind 2/3/10 Basic...

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