weathertwo1011

weathertwo1011 - And The Weather’s Good…part II And The...

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Unformatted text preview: And The Weather’s Good…part II And The Weather’s Good…part II AP Env Sci 2010­2011 Wind Wind • ALL wind is caused by horizontal differences in air pressure • What is Air Pressure? – – – Pressure exerted by the weight of air above What is the pressure in here? What units are used for air pressure? (Force/area) millibar = 100 N/m2 – Pressure is set by Temperature and Density of air • Higher Pressure Difference, More Wind What causes the pressure differences? What causes the pressure differences? • Uneven Heating of the Earth’s Surfaces • Demonstrations: – Sea Breeze – Land Breeze • Temperature Variation ­> Pressure Variation ­> Wind If Pressure Acted Alone… If Pressure Acted Alone… • • • If Earth did not rotate If there was no friction Then, air would always flow directly from High pressure to Low pressure • In Reality, three factors control wind: – Pressure Differences – Coriolis Effect – Friction Earth without Rotation… • http://teachingboxes.org/catalog.jsp?id=TBOXR­000­000­000­039 Rotating Earth – What Does it Do? Rotating Earth – What Does it Do? • Coriolis Effect: – All free moving objects (wind, planes) are deflected right of their path of motion in Northern Hemisphere, left of path of motion in Southern Hemisphere • Video • Demo: Earth viewed from North Pole Results of the Coriolis Effect Results of the Coriolis Effect Friction Friction • Most important for air contacting a surface • Winds aloft – not affected • At surface, friction slows winds Some “Local” Winds Some “Local” Winds • Land and Sea Breezes • Mountain and Valley Breezes • • – Valley breeze: Sun heats air along slopes more intensely, rises – At night, mountain breeze Chinook: warm, dry air descending mountain – Pulled over mountain by low pressure system – Air is heated by compression as it flows downward Katabatic Winds: – Cold air over ice­covered highland “falls” downhill under influence of gravity – Antarctica: up to 66 ft/sec Global Winds to Know Global Winds to Know Image/Text/Data from the University of Illinois WW2010 Project ...
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