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Local and Global Winds ► AIM: How is wind created? Do Now: ► Recall what creates areas of higher and lower air pressure. ► **FACT** Higher pressure air (H) is cooler, more clear, and drier than Lower pressure air (L) which is warmer, cloudier, and more moist. Vocabulary ► Air pressure ► Local winds ► Global winds ► Prevailing westerlies ► Isobars ► Cyclones ► Anti-cyclones ► Wind Chill factor ► Anemometer ► Wind Vane 1. What is wind? ► Wind – the horizontal movement of air ► ***Wind is created when the uneven heating of Earth’s surfaces creates areas of high and low pressure***. ► Air likes to move from Higher pressure (H) to Lower pressure (L) 2. How is wind named and measured? ► Named by the direction and speed from which it comes. Ex. Westerly wind comes from the West ► Anemometer – measures wind speed using cups connected to a speedometer ► Wind vane – points to direction that wind comes from 3. What are local winds? a. Local winds blow over short distances. b. Part of the weather report. weather.com c. Examples: Land breezes, sea breezes ► Observe an animation of land and sea breezes. 4. Sea and Land Breezes ► During day, warmer air rises over the sand, cooler air sinks over sea. ► Air moves from water to land = sea breeze L H ► During night, cooler air sinks over the sand, warmer air rises over sea. ► Air moves from land to sea = land breeze H L Sea and Land breezes are local winds that affect us near TOBAY or Jones Beach 5. Larger local breezes ► Monsoon – sea or land breezes covering a large area that change directions with the seasons (Southeast Asia) Monsoons ► Winter: A large land breeze, sinking higher pressure air over land keeps moist air off shore =Good weather ► Summer: A large sea breeze, rising, moist air from over the ocean blows onto land = Bad weather, rain 6. Global Winds ► Global winds blow over a long distance from a specific direction ► Created by uneven heating of equator and poles H = poles, cool, sinking L = equator, warm, rising ► Weather patterns are affected by the prevailing winds in an area. Name the prevailing winds that affect each area…ESRT pg 14 ► Latitude – distance from Equator ► Horse latitudes – areas where air sinks, at 30°N and 30°S ► Doldrums – areas with little wind (at the Equator) 7. Global Convection Currents ► Poles have higher pressure (cold air) ► Equator has lower pressure (warmer air) ► Air sinks from poles Equator creating convection cells Bands of H and L air are created The convection currents create a distribution system for earth’s heat http://www.youtube.c om/watch?v=QbvHglF yZbg&playnext=1&list =PL9014F9D9475764 97 8. Why do the winds curve? a. The Earth’s rotation curves the global winds. ► Right in the Northern hemisphere Left in the Southern hemisphere ► a. This is called Coriollis Effect. ► Coriolis Force: an artifact of the earth's rotation Observe an animation of the Coriolis effect over Earth's surface. ► ► Jet 9. Jet Streams stream – bands of high speed winds ► 200 to 400 kilometers/hour ► Up near the Tropopause ► Can “stear” weather and pollution patterns http://www.youtube.com/watc h?v=CgMWwx7Cll4 http://www.youtube.co m/watch?v=UFC6819LS 5w&feature=related ESRT pg 14. Question… ► Why do you think there are bands of wet and dry air at the equator, 30o, 60o and 90 o? 10. Wind Chill factor ► Wind chill factor – increased cooling, increased evaporation, make the temperature feel colder. The stronger the wind, the colder you feel! Summary: What affect do winds have on weather? Moves weather b. Creates weather patterns (seasonal changes) c. Increases evaporation (dry things out) d. Creates a wind chill (colder temperatures) a. http://www.youtube.com/watch?v=kPueXIHGQrg&feature=related http://www.youtube.com/watch?v=fYfrWLhZy1A&feature=related Pressure, Wind and Weather Maps show us where the rising and sinking air is….. High vs. Low Air High: Anticyclone Clockwise, outward More dense Air sinks Good weather Dry air ► Lows : Cyclones Counter clockwise, inward Less Dense Rising air Moist air Bad weather Warm air rises, cool air sinks Isobars ► Isobars are lines on a map that connect areas of equal air pressure. ► Same rules apply…. Connect equal values Calculate gradient Steep side where lines are closest together Air moves from H to L Pressure gradients ► Pressure Gradient - the change in air pressure with distance. ► The windiest areas have the steepest gradients. ► Calculate the gradient between A – B and C – D on the following map A D B C Wind barbs ► Tell us direction and speed. The wind is blowing from the southeast at 1520 mph Draw the isobars Barometric pressure on station models In the plotted station model the 3 digit number to the upper right of the station circle is the barometric pressure. It will look like 196 for pressures 1000 millibars and higher: and 992 for pressures below 1000. So, 196 means 1019.6 mb and 992 means 999.2 mb. Basically, add a 10 in front of anything starting with a 0 or 1, and a 9 for anything starting with a 9. Convert each station and then draw the isobars. 1016, 1012, 1008 and 996, 1004, 1008 1016 mb H L 996 mb 1012 mb 1000 mb 1008 mb 1004 mb