Chapter 7: Atmospheric circulations Scales of atmospheric motions Scales of atmospheric motions...
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Transcript of Chapter 7: Atmospheric circulations Scales of atmospheric motions Scales of atmospheric motions...
Chapter 7: Chapter 7: Atmospheric Atmospheric circulationscirculations
Scales of atmospheric motionsScales of atmospheric motions Eddies - big and smallEddies - big and small Local wind systemsLocal wind systems Global windsGlobal winds Global wind patterns and the oceansGlobal wind patterns and the oceans
Scales of Scales of atmospheric atmospheric
motionsmotions
Scales of atmospheric Scales of atmospheric motionsmotions
scales of motionscales of motion microscalemicroscale synoptic scalesynoptic scale planetary scaleplanetary scale
• Lots of important weather events occur on microscales, likeLots of important weather events occur on microscales, likeevaporation of liquid water molecules from the earth’s surfaceevaporation of liquid water molecules from the earth’s surface
Eddies - big and Eddies - big and smallsmall
Eddies - big and smallEddies - big and small
eddyeddy rotorrotor wind shearwind shear turbulenceturbulence
• wind shear can sometimes be observed by watching thewind shear can sometimes be observed by watching themovement of clouds at different altitudesmovement of clouds at different altitudes
Local wind Local wind systemssystems
Thermal circulationsThermal circulations
isobars and density differencesisobars and density differences thermal circulationsthermal circulations
Sea and land breezesSea and land breezes
sea breezesea breeze land breezeland breeze sea breeze frontsea breeze front Florida sea breezesFlorida sea breezes
• Sea and land breezes also occur near the shores of largeSea and land breezes also occur near the shores of largelakes, such as the Great Lakeslakes, such as the Great Lakes
Seasonally changing Seasonally changing winds - the monsoonwinds - the monsoon
Monsoon wind systemMonsoon wind system Asian monsoonAsian monsoon other monsoonsother monsoons
Mountain and valley Mountain and valley breezesbreezes
valley breezevalley breeze mountain breezemountain breeze
• The nighttime mountain breeze is sometimes calledThe nighttime mountain breeze is sometimes calledgravity winds or drainage winds, because gravitygravity winds or drainage winds, because gravitycauses the cold air to ‘drain’ downhillcauses the cold air to ‘drain’ downhill
Katabatic windsKatabatic winds
drainage windsdrainage winds borabora
• Katabatic winds are quite fierce in parts of Antarctica, withKatabatic winds are quite fierce in parts of Antarctica, withhurricane-force wind speeds. hurricane-force wind speeds.
Chinook (Foehn) windsChinook (Foehn) winds
Chinook windsChinook winds compressional heatingcompressional heating chinook wall cloudchinook wall cloud
• In Boulder, Colorado, along the eastern flank of the In Boulder, Colorado, along the eastern flank of the Rocky Mountains, chinook winds are so common thatRocky Mountains, chinook winds are so common thatmany houses have sliding wooden shutters to protectmany houses have sliding wooden shutters to protecttheir windows from windblown debris.their windows from windblown debris.
Santa Ana windsSanta Ana winds
Santa Ana windSanta Ana wind compressional heatingcompressional heating wildfireswildfires
• Many Southern California residents regularly hose downMany Southern California residents regularly hose downtheir roofs to prevent fires during Santa Ana wind seasontheir roofs to prevent fires during Santa Ana wind season
Desert windsDesert winds
dust stormsdust storms dust devilsdust devils
Global windsGlobal winds
General circulation of General circulation of the atmospherethe atmosphere
cause: unequal heating of the earth’s cause: unequal heating of the earth’s surfacesurface
effect: atmospheric heat transporteffect: atmospheric heat transport
• Ocean currents also transport heat from the equator toOcean currents also transport heat from the equator tothe poles and back.the poles and back.
Single-cell modelSingle-cell model
basic assumptionsbasic assumptions Hadley cellHadley cell why the single-cell model is wrongwhy the single-cell model is wrong
• One of the world’s premier atmospheric science research facilities,One of the world’s premier atmospheric science research facilities,the Hadley Centre for Climate Research, is named after George Hadleythe Hadley Centre for Climate Research, is named after George Hadley
Three-cell modelThree-cell model model for a rotating earthmodel for a rotating earth Hadley cellHadley cell doldrumsdoldrums subtropical highssubtropical highs trade windstrade winds intertropical convergence intertropical convergence
zonezone westerlieswesterlies polar frontpolar front polar easterliespolar easterlies
• many global circulation terms,many global circulation terms,including ‘trade winds’ and including ‘trade winds’ and ‘doldrums’, were named by ‘doldrums’, were named by mariners who were well acquaintedmariners who were well acquaintedwith wind patternswith wind patterns
Average surface winds Average surface winds and pressure: the real and pressure: the real
worldworld semipermanent highs and lowssemipermanent highs and lows Bermuda high & Pacific highBermuda high & Pacific high Icelandic low & Aleutian lowIcelandic low & Aleutian low Siberian highSiberian high
• The Bermuda High frequently brings hot, muggy weatherThe Bermuda High frequently brings hot, muggy weatherto the eastern USto the eastern US
The general circulation The general circulation and precipitation and precipitation
patternspatterns major controlsmajor controls ITCZ, midlatitude storms, polar frontITCZ, midlatitude storms, polar front
• Most of the world’s thunderstorms are found along the ITCZMost of the world’s thunderstorms are found along the ITCZ
Westerly winds and the Westerly winds and the jet streamjet stream
jet streamsjet streams subtropical jet streamsubtropical jet stream polar front jet streampolar front jet stream
Global wind Global wind patterns and the patterns and the
oceansoceans
Winds and upwellingWinds and upwelling
upwellingupwelling wind flow parallel to the coastlinewind flow parallel to the coastline
• upwelling frequently occurs along the coastupwelling frequently occurs along the coastof Californiaof California
El Niño and the southern El Niño and the southern oscillationoscillation
El Niño eventsEl Niño events Southern OscillationSouthern Oscillation La NiñaLa Niña teleconnectionsteleconnections
• ENSO is an example of a global-scale weather phenomenonENSO is an example of a global-scale weather phenomenon
Other atmosphere-ocean Other atmosphere-ocean interactionsinteractions
North Atlantic OscillationNorth Atlantic Oscillation Arctic OscillationArctic Oscillation Pacific Decadal OscillationPacific Decadal Oscillation
• Other atmosphere-ocean interactions may very well beOther atmosphere-ocean interactions may very well bediscovered in the coming yearsdiscovered in the coming years