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Global-scale Winds Courtesy: U. of Alaska

Global-scale Winds Courtesy: U. of Alaska. General Circulation > Global wind systems General circulation 1-cell, 3-cell models, comparison to real world > Semi-permanent pressure features > Jet streams. 02.23.2010. Scales of Motion - Hierarchy. Longwaves. planetary scale.

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Global-scale Winds Courtesy: U. of Alaska

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  1. Global-scale WindsCourtesy: U. of Alaska General Circulation> Global wind systems General circulation 1-cell, 3-cell models, comparison to real world> Semi-permanent pressure features> Jet streams 02.23.2010

  2. Scales of Motion - Hierarchy Longwaves planetaryscale Weather MapHighs and Lows Weather fronts synopticscale HurricanesTopical storms Land/sea breezeMtn/Valley breezeChinookSanta Ana ThunderstormsTornadoesWaterspoutsDust devils mesoscale Small turbulenteddies microscale secondstominutes minutestohours hourstodays daystoweeks

  3. COLD UNEQUAL HEATINGOF THE EARTHTHERMAL IMBALANCE WARM COLD Atmospheric General Circulation + Large-scale, hemispheric flow + DRIVING FORCE??+ Average wind patterns across globe + Interrupted by highs and lowsmoving through

  4. Net LOSS Net GAIN Net LOSS Energy Imbalance Driver of Atmospheric Circulation Atmospheric General Circulation UNEQUAL HEATING OF THE EARTH THERMAL IMBALANCE COLD WARM COLD

  5. COLD WARM COLD Models of Atmospheric Circulation Single-cell ModelAssume1) aqua planet2) sun over equator 3) non-rotating earth

  6. pressure high low Models of Atmospheric Circulation 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 The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001

  7. Models of Atmospheric Circulation Three-cell ModelAssume1) aqua planet2) sun over equator 3) non-rotating earth Result>excessive heating at equator >thermally-driven convection cells >deflection of winds >Hadley cell Ferrel cell Polar cell The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001

  8. Atmospheric Circulation Models vs Reality Idealized winds Actual winds The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001

  9. Atmospheric Circulation Models vs Reality Why the difference? 1) land-water distribution 2) seasonality unequal heating/cooling rates Actual winds Idealized winds

  10. Atmospheric Circulation Some Features of Note:Equatorial • ITCZ (Intertropical Convergence Zone) • Equatorial low • Area of low wind speed Doldrums (weak PG)

  11. Atmospheric Circulation Some Features of Note:Subtropics • Trade winds • Horse latitudesweak winds • Subtropical highwarm and dryDesert areas of the world

  12. Atmospheric Circulation Some Features of Note:Midlatitudes, Polar • Prevailing westerlies • Polar front and areas of low pressure • Polar easterlies

  13. Persistent Circulation PatternsNHwinter Sea level pressure and prevailing winds

  14. Persistent Circulation PatternsNHwinter > subtropical highs Sea level pressure and prevailing winds

  15. Persistent Circulation PatternsNHwinter > 2 major subpolar lows: near polar front, storm track Sea level pressure and prevailing winds

  16. Persistent Circulation PatternsNHwinter > subpolar highs: shallow, thermally induced Sea level pressure and prevailing winds

  17. Persistent Circulation PatternsNHwinter > subpolar trough in SH: high winds and seas, roaring 40s Sea level pressure and prevailing winds

  18. Persistent Circulation PatternsNHwinter > ITCZ displaced south Sea level pressure and prevailing winds

  19. Persistent Circulation PatternsNHsummer > ITCZ displaced north Sea level pressure and prevailing winds

  20. Persistent Circulation PatternsNHsummer > Subtropical highs move north Sea level pressure and prevailing winds

  21. Persistent Circulation PatternsNHsummer > Thermal lows develop over land Sea level pressure and prevailing winds

  22. Persistent Circulation PatternsNHsummer > Weak Icelandic Low remains, Aleutian Low disappears Sea level pressure and prevailing winds

  23. Persistent Circulation PatternsNHsummer > Asian Monsoon season Sea level pressure and prevailing winds

  24. summer Subpolar lows disappear Subtropical highs remain Zone of max heating shifts northWeak equator - pole temp gradient Seasonal Circulation Patterns winter Strong thermal imbalanceStrong pressure gradient Strong windsStrong equator - pole temp gradient Thermal Imbalance is the Driver Sea level pressure and prevailing winds

  25. Seasonal Circulation Animation L H Sea level pressure and windsUniversity of Oregon Thermal Imbalance is the Driver

  26. Dry Wet Wet Wet Wet Dry Dry Dry Dry Dry seasonally Dry Dry General Circulation and Precipitation Wet Wet Wet

  27. General Circulation and Precipitation Dry Wet Precipitation (mm)University of Oregon

  28. 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

  29. Jet Streams • Mark boundary between surface air masses • Shows ridges, troughs, eddies • Changes in space and time

  30. Jet Streams • Seasonality • Note the speeddifferences • Surface temperature differences • Tend to steer storm tracks

  31. Jet Streams

  32. Jet Streaks

  33. Jet Stream and Jet Travel

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