Global and Local Winds


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Global and Local Winds

  1. 1. WindsWinds
  2. 2. Wind is theWind is the horizontalhorizontal movement of air frommovement of air from an area ofan area of highhigh pressure to an area ofpressure to an area of lowlow pressure.pressure. All winds are causedAll winds are caused by differences inby differences in airair pressurepressure  Most differences in airMost differences in air pressure are due topressure are due to unequalunequal heatingheating in thein the atmosphereatmosphere  Water has a higherWater has a higher specific heatspecific heat thanthan sand, so it heats muchsand, so it heats much slower.slower.  CoolCool, dense air sinks, dense air sinks and has higher airand has higher air pressurepressure  WarmWarm, less dense air, less dense air rises and has lowerrises and has lower pressurepressure
  3. 3. Why Air Moves  Air Rises at the Equator and Sinks at the Poles As the cold air sinks, it creates areas of high pressure around the poles. This cold polar air then flows toward the equator.  Pressure Belts Are Found Every 30º Convection cells are separated by pressure belts, bands of high and low pressure.
  4. 4. Global WindsGlobal Winds  Caused by globalCaused by global convection currentsconvection currents..  They blow steadily fromThey blow steadily from specific directions overspecific directions over great distances.great distances.  The high pressure coolThe high pressure cool air at the poles tries to fillair at the poles tries to fill in the low pressure areasin the low pressure areas at the the equator.  This causes theThis causes the globalglobal winds.winds.  This is why the weatherThis is why the weather systems tend to alwayssystems tend to always come from west to east income from west to east in Georgia.Georgia.
  5. 5. Polar EasterliesPolar Easterlies  Wind belts thatWind belts that extend from theextend from the poles topoles to 6060°° latitudelatitude  Formed from coldFormed from cold sinking air movingsinking air moving from the polesfrom the poles creatingcreating coldcold temperaturestemperatures
  6. 6. WesterliesWesterlies Wind belts foundWind belts found between 30between 30°° and 60° latitudeand 60° latitude Flow towardsFlow towards the poles fromthe poles from west to eastwest to east carryingcarrying moistmoist airair over theover the United StatesUnited States
  7. 7. Trade WindsTrade Winds Winds that blowWinds that blow fromfrom 3030° almost° almost to the equatorto the equator Called the tradeCalled the trade winds because ofwinds because of their use bytheir use by earlyearly sailorssailors
  8. 8. Doldrums and Horse LatitudesDoldrums and Horse Latitudes DoldrumsDoldrums  Located along theLocated along the equator whereequator where nono winds blowwinds blow because the warmbecause the warm rising air createsrising air creates and area of lowand area of low pressurepressure Horse LatitudesHorse Latitudes  Occur at about 30Occur at about 30° north° north and south of the equatorand south of the equator where the winds arewhere the winds are very weakvery weak  Most deserts on theMost deserts on the Earth are located hereEarth are located here because of thebecause of the dry airdry air
  9. 9. Jet StreamJet Stream  The jet streams areThe jet streams are narrow belts ofnarrow belts of high speedhigh speed windswinds that blow in thethat blow in the upperupper tropospheretroposphere and lowerand lower stratospherestratosphere  SeparatesSeparates warmwarm air from cold airair from cold air
  10. 10. Pressure CellsPressure Cells  The earth isThe earth is encircled byencircled by several broadseveral broad prevailing windprevailing wind belts.belts.  The threeThe three primaryprimary circulation cellscirculation cells are known asare known as the:the: HadleyHadley cell;cell; FerrelFerrel cell; andcell; and PolarPolar cell.cell.
  11. 11. Why Air Moves, continued • The Coriolis Effect The apparent curving of the path of currents due to the Earth’s rotation is called the Coriolis effect. • This causes winds to curve to the right in the northern hemisphere, and the opposite in the southern hemisphere.
  12. 12. Measuring WindsMeasuring Winds  Winds are described byWinds are described by theirtheir directiondirection and speedand speed  A windA wind vanevane determinesdetermines wind directionwind direction  The name of a wind is theThe name of a wind is the direction it is coming fromdirection it is coming from so a north wind is fromso a north wind is from thethe northnorth. It is headed to. It is headed to thethe southsouth..  Wind speed is measuredWind speed is measured with anwith an anemometeranemometer..
  13. 13. Local winds are. . .Local winds are. . .  Winds that blow overWinds that blow over shortshort distancesdistances  Caused byCaused by unequalunequal heating of the earth’sheating of the earth’s surface within a smallsurface within a small areaarea  This creates localThis creates local convection currents.convection currents.  Form only when no windsForm only when no winds are blowing from far awayare blowing from far away
  14. 14. Sea BreezeSea Breeze  In the morning the sandIn the morning the sand heats up much faster thanheats up much faster than the water, so the airthe water, so the air above the sand is hotter.above the sand is hotter.  Hotter air is less dense, soHotter air is less dense, so it rises.  The cooler air over theThe cooler air over the ocean will push in to causeocean will push in to cause the hot air to rise.the hot air to rise.  So in the morning the windSo in the morning the wind is in your face as you faceis in your face as you face the ocean.the ocean.
  15. 15. Sea Breeze 2Sea Breeze 2  1. Warm air1. Warm air over land risesover land rises  2. Sea Breeze2. Sea Breeze moves inlandmoves inland  3. Cumuli3. Cumuli develop aloftdevelop aloft and moveand move seawardseaward  4. Upper level4. Upper level return landreturn land breezebreeze  5. Cool air5. Cool air aloft sinks overaloft sinks over waterwater  6. Sea Breeze6. Sea Breeze
  16. 16. Land BreezeLand Breeze  At night, the sand coolsAt night, the sand cools very quickly, while thevery quickly, while the ocean temperature changesocean temperature changes very little.very little.  So the warm air over theSo the warm air over the ocean rises, pushed up byocean rises, pushed up by the cooler air over thethe cooler air over the beach.beach.  So the wind will hit yourSo the wind will hit your back as you look out overback as you look out over the ocean at night.the ocean at night.
  17. 17. Land Breeze 2Land Breeze 2  1. Cool air over1. Cool air over land sinksland sinks  2. Land Breeze2. Land Breeze moves out overmoves out over waterwater  3. Relatively3. Relatively warmer waterwarmer water heats air whichheats air which then risesthen rises  4. Upper level4. Upper level return sea breezereturn sea breeze  5. Cool air over5. Cool air over land sinksland sinks
  18. 18. Sea/Land BreezesSea/Land Breezes