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Transcript of Global-scale Winds Courtesy: U. of Alaska 02.23.2010 General Circulation > Global wind systems...
![Page 1: Global-scale Winds Courtesy: U. of Alaska 02.23.2010 General Circulation > Global wind systems General circulation 1-cell, 3-cell models, comparison to.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649ea25503460f94ba5b2f/html5/thumbnails/1.jpg)
Global-scale WindsCourtesy: U. of Alaska
02.23.2010
General Circulation
> Global wind systems General circulation 1-cell, 3-cell models, comparison to real world
> Semi-permanent pressure features
> Jet streams
![Page 2: Global-scale Winds Courtesy: U. of Alaska 02.23.2010 General Circulation > Global wind systems General circulation 1-cell, 3-cell models, comparison to.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649ea25503460f94ba5b2f/html5/thumbnails/2.jpg)
Scales of Motion - Hierarchy
Small turbulenteddies
ThunderstormsTornadoes
WaterspoutsDust devils
Land/sea breezeMtn/Valley breeze
ChinookSanta Ana
HurricanesTopical storms
Weather MapHighs and LowsWeather fronts
Longwaves
secondsto
minutes
minutesto
hours
hoursto
days
daysto
weeks
microscale
mesoscale
synopticscale
planetaryscale
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Atmospheric General Circulation
+ Large-scale, hemispheric flow + DRIVING FORCE??+ Average wind patterns across globe
+ Interrupted by highs and lowsmoving through
UNEQUAL HEATINGOF THE EARTH
THERMAL IMBALANCE
WARM
COLD
COLD
![Page 4: Global-scale Winds Courtesy: U. of Alaska 02.23.2010 General Circulation > Global wind systems General circulation 1-cell, 3-cell models, comparison to.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649ea25503460f94ba5b2f/html5/thumbnails/4.jpg)
Atmospheric General CirculationUNEQUAL HEATING OF THE EARTH
THERMAL IMBALANCE
WARM
COLD
COLD
Net GAIN
Net LOSS
Net LOSS
Energy Imbalance Driver of Atmospheric Circulation
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Models of Atmospheric CirculationSingle-cell ModelAssume1) aqua planet2) sun over equator 3) non-rotating earth
WARM
COLD
COLD
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Single-cell ModelAssume1) aqua planet2) sun over equator 3) non-rotating earth
Result>excessive heating at equator
>thermally-driven convection cell
>pole-ward flow aloft equator-ward flow sfc
>termed, Hadley cell
Models of Atmospheric Circulation
pressure
low
high
The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001
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Three-cell ModelAssume1) aqua planet2) sun over equator 3) non-rotating earth3) non-rotating earth
Result>excessive heating at equator
>thermally-driven convection cells
>deflection of winds
>Hadley cell Ferrel cell Polar cell
Models of Atmospheric Circulation
The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001
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Atmospheric Circulation Models vs Reality
The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001
Idealized winds Actual winds
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Atmospheric Circulation Models vs Reality
Idealized winds
Actual winds Why the difference?1) land-water distribution2) seasonality
unequal heating/cooling rates
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Atmospheric Circulation
Some Features of Note:Equatorial
•ITCZ (Intertropical Convergence Zone)
•Equatorial low
•Area of low wind speed Doldrums (weak PG)
![Page 11: Global-scale Winds Courtesy: U. of Alaska 02.23.2010 General Circulation > Global wind systems General circulation 1-cell, 3-cell models, comparison to.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649ea25503460f94ba5b2f/html5/thumbnails/11.jpg)
Atmospheric Circulation
Some Features of Note:Subtropics
•Trade winds
•Horse latitudesweak winds
•Subtropical highwarm and dryDesert areas of the world
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Atmospheric Circulation
Some Features of Note:Midlatitudes, Polar
•Prevailing westerlies
•Polar front and areas of low pressure
•Polar easterlies
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Sea level pressure and prevailing winds
Persistent Circulation Patterns NH winter
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Persistent Circulation Patterns NH winter
Sea level pressure and prevailing winds
> subtropical highs
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Persistent Circulation Patterns NH winter
Sea level pressure and prevailing winds
> 2 major subpolar lows: near polar front, storm track
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Persistent Circulation Patterns NH winter
Sea level pressure and prevailing winds
> subpolar highs: shallow, thermally induced
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Persistent Circulation Patterns NH winter
Sea level pressure and prevailing winds
> subpolar trough in SH: high winds and seas, roaring 40s
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Persistent Circulation Patterns NH winter
Sea level pressure and prevailing winds
> ITCZ displaced south
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Persistent Circulation Patterns NH summer
Sea level pressure and prevailing winds
> ITCZ displaced north
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Persistent Circulation Patterns NH summer
Sea level pressure and prevailing winds
> Subtropical highs move north
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Persistent Circulation Patterns NH summer
Sea level pressure and prevailing winds
> Thermal lows develop over land
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Persistent Circulation Patterns NH summer
Sea level pressure and prevailing winds
> Weak Icelandic Low remains, Aleutian Low disappears
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Persistent Circulation Patterns NH summer
Sea level pressure and prevailing winds
> Asian Monsoon season
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Seasonal Circulation Patterns
Sea level pressure and prevailing winds
winter summer
Subpolar lows disappearSubtropical highs remainZone of max heating shifts northWeak equator - pole temp gradient
Strong thermal imbalanceStrong pressure gradientStrong windsStrong equator - pole temp gradient
Thermal Imbalance is the Driver
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Seasonal Circulation Animation
Sea level pressure and windsUniversity of Oregon
Thermal Imbalance is the Driver
L
H
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General Circulation and Precipitation
Wet
Wet
Wet
Dry
Dry
Dry
DryWet Dry
Wet Dry
Wet Dry
Wet Dry
seasonally
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General Circulation and Precipitation
Precipitation (mm)University of Oregon
Dry
Wet
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Jet Streams
• Fast-moving rivers of air
• High altitudes (~ 35000 ft) near tropopause
• Long, shallow, narrow moving west to east
• First observed during WW II
• Suspected earlier from ground observations of fast-moving cirrus
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Jet Streams
• Mark boundary between surface air masses
• Shows ridges, troughs, eddies
• Changes in space and time
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Jet Streams
• Seasonality
• Note the speeddifferences
• Surface temperature differences
• Tend to steer storm tracks
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Jet Streams
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Jet Streaks
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Jet Stream and Jet Travel