2Why Air Moves Wind is created by differences in air pressure Bigger difference = faster windCaused by unequal heating of earth
3Air The air by the equator is warm and rises Low pressureThe air by the poles is cold and denseHigh pressureWind will then travel from poles to equatorMove from area of high pressure to area of low
4Pressure Belts Wind travels in small belt patters It never travels too far because it will cool as it moves and sink back downMoves at a about 30 degrees at a time or down the earth
5Earth’s rotation affects wind direction Without the earths rotation the global winds would flow directly from the poles to the equator.Coriolis EffectInfluence of Earth’s rotation on objects that move over Earth.
6The Coriolis Effect The wind does not travel perfectly north to south Earth’s rotation causes wind to travel in a curved path
7Coriolis Effect Global winds curve as Earth turns beneath them. Northern HemisphereWinds curve to the rightSouthern HemisphereWinds curve to the leftOnly noticeable for winds that travel long distances.Causes global winds to travel along 3 routes in each hemisphereRoutes are called global wind belts
8Types of Wind Local wind Global wind Both caused by uneven heating Sea BreezeLand BreezeMonsoon – Seasonal changes in windGlobal windDoldrums / Horse LatitudesEasterlies / WesterliesJet StreamBoth caused by uneven heating
9Global Winds The distance winds travel varies. Sunlight is concentrated near the equator because it strikes the surface directlyThe distance winds travel varies.Some winds die out quicklyGlobal windsWinds that travel long distances in steady patterns over several weeksCaused by uneven heating between the equator and the north and south polesSunlight is more spread out near the poles because it strikes at a lower angle
10Global Winds Continued Near the equator concentrated sunlight heats the surface to a high temperature. Warm air rises, producing low pressure.In regions closer to the poles, the sunlight is more spread out. The air above them is cooler and dense. Sinking dense air produces high pressure that sets global winds in motion.
11Calm Regions Doldrums Horse Latitudes Low-pressure zones near equator The rising, moist air produces clouds and heavy rain.Horse LatitudesHigh-pressure zones located 30 degrees north and south of the equator.Clear and dry weather
12Wind Belts Coriolis effect creates 3 wind belts in each hemisphere Trade WindsBlow from east. Move towards equator. Die out as they near the equatorWesterliesBlow from the west. Move towards the poles. Brings storms across much of the U.S.EasterliesBlow from the east. Move towards mid-latitudes. Storms occur when cold air from easterlies meets the warm air of the westerlies.
15Effects of Wind on Travel How would wind effect travel?Sailors used to dread traveling through the doldrums and the horse latitudes because there wasn’t enough wind.To avoid the calm regions, sailors sought out global wind beltsSailors rely on trade winds to get across the ocean
16Jet streams flow near the top of the troposphere Flow in upper troposphereTravels west to eastOften moves at high speeds (greater than 124 mi/hr).Form because Earth’ssurface is heatedunevenly.Loop north and south
17Jet Streams Each hemisphere has 2 jet streams Subtropical jet stream Flow closer to poles in SUMMERPolar jet streamHas a strong influence of weatherCan pull cold air down from Canada or pull warm air up.Strong storms form along its loops
18Patterns of heating and cooling cause local winds Some winds change daily in a regular pattern.Blow within small areasLand breezes and Sea breezes are similar but opposite.
20Land Breeze Wind blows from the land to the ocean Happens during the NightLand cools down causing it to have a low air pressureWater maintains its temperature causing it to have a higher air pressureAir will move from high pressure to low pressureIt will move from the land to water