Ch08_Press-wind_107 - Ch 8 Air Pressure and Winds 8.1...

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Ch. 8 Air Pressure and Winds 8.1 Atmospheric Pressure 8.2 Pressure Gradient and Coriolis Forces 8.3 Geostrophic and Gradient Winds
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Why Does the Wind Blow? What is wind? Wind is horizontally movement of air Why does air move? Air moves in response to horizontal gradient in air pressure force, attempting to equalize imbalances in pressure Which wind direction, from or to? from which the wind is blowing http://www.eo.ucar.edu/basics/wx_2_c.html
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How Much Pressure Are We Under? Pressure is the force exerted on objects by the weight of tiny molecules of air How heavy is the pressure? - 1 ton per square ft http://www.youtube.com/watch?v=QVayky_b-6U An Experiment Boil a small amount of water in a soda can until the can is full of water vapor Then flip the can into a pan of ice water What will happen?
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Measuring Air Pressure Mercury Barometer Aneroid Barometer The instruments that measure air pressure are called barometer
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Measuring Air Pressure –cont’d Bad weather – low pressure High altitude – low pressure Sea level – standard
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Surface and Sea Level Pressures Pressure decreases with elevation by about 1 millibar per 10 meter Pressure at different altitudes is incomparable We extrapolate pressure from ground surface to sea level – a common level.
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Sea Level Pressure Sample of sea level pressure map or chart The contours are isobars along which pressure value is constant The numbers at stations are sea level pressure in millibar (mb). 1 0 2 6 8
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Pressure and Temperature Pressure relates to density; density relates temperature Colder air – molecules move more slowly and are closer together (more dense – column contracts) Warmer air – molecules move faster and are further apart (less dense – column expands)
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Wrap Up - Pressure Pressure is the weight of air above a given level It decreases with height rapidly; the higher elevation; the lower pressure Pressure is used to represent vertical coordinate, instead of altitude we used so far
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This note was uploaded on 03/18/2012 for the course UNDERSTAND 212 taught by Professor Qi during the Spring '12 term at Saint Louis.

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Ch08_Press-wind_107 - Ch 8 Air Pressure and Winds 8.1...

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