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ATM S 542 Synoptic Meteorology Overview

ATM S 542 Synoptic Meteorology Overview. Gregory J. Hakim University of Washington, Seattle, USA. www.atmos.washington.edu/~hakim. Vertical structure of the atmosphere. Atmospheric phenomena by horizontal scale. Potential vorticity. Tropopause. Overview. Asymptotic methods

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ATM S 542 Synoptic Meteorology Overview

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  1. ATM S 542 Synoptic Meteorology Overview Gregory J. Hakim University of Washington, Seattle, USA www.atmos.washington.edu/~hakim • Vertical structure of the atmosphere. • Atmospheric phenomena by horizontal scale. • Potential vorticity. • Tropopause.

  2. Overview • Asymptotic methods • expand dependent variables in a power series. • small parameters needed. • co-operative dialog between math & physics is helpful. • Role of asymptotics in atmosphere/ocean dynamics. • simplified equations for solution & understanding. • Goals • survey atmosphere/ocean structure & phenomena. • bias toward extratropics & atmosphere. • motivate asymptotic methods for these problems. Gregory J. Hakim (U. Washington)

  3. Jets, stirring, organized structures; waves, vortices, convection. Gregory J. Hakim (U. Washington)

  4. Atmospheric Structure • Atmosphere: very thin gas layer. • depth <<< radius earth. • Troposphere: “weather layer” • ~ 10 km deep. • ~ 80% mass of atmosphere. • ~ all H2O vapor. • Tropopause: jet streams. • wave guide. • unstable: cyclones. Gregory J. Hakim (U. Washington)

  5. Atmospheric Energy Spectrum Energy increases with horizontal length scale. Gregory J. Hakim (U. Washington)

  6. Planetary waves L ~ 10 000 km H/L ~ .001 Ro ~ 0.01 Cyclones L ~ 1000 km H/L ~ .01 Ro ~ 0.1 Gravity waves L ~ 10--100 km H/L ~ .1-1 Ro ~ 1 Convection L ~ 10 km H/L ~ 1 Ro > 1 Atmospheric Phenomena by Scale Long, slow Short, fast Gregory J. Hakim (U. Washington)

  7. Jet streams & planetary waves Gregory J. Hakim (U. Washington)

  8. Jet Streams Gregory J. Hakim (U. Washington)

  9. Jets: ~ Geostrophic Balance Gregory J. Hakim (U. Washington)

  10. Jet stream vorticity Waves & particles Waves: Information flows through the medium by radiation. Particles (vortices): Information flows through the medium by material transport. Gregory J. Hakim (U. Washington)

  11. Cyclones & Anticyclones Gregory J. Hakim (U. Washington)

  12. Cyclone Structure • Center has lowest pressure. • ~geostrophic winds. • Warm air moves poleward. • and upward. • warm front. • Cold air moves equatorward. • and downward. • cold front. • Clouds & precipitation. • ~ “comma” shape. Gregory J. Hakim (U. Washington)

  13. North American Cyclone Gregory J. Hakim (U. Washington)

  14. Pacific Extratropical Cyclone • Intense vortex • Cold air: shallow cellular convection • Warm air: stratiform cloud • Sharp frontal boundaries L Zoom in on cold front… Gregory J. Hakim (U. Washington)

  15. Scale collapse at cold front: “rope cloud”---narrow line convection. Gregory J. Hakim (U. Washington)

  16. Cyclone—Anticyclone Track Density Hoskins & Hodges (2002) Primary tracks coincide with time-mean jet stream locations. Gregory J. Hakim (U. Washington)

  17. Jet-Level 2.5—6 d Variance Maximum variance in storm tracks. Hoskins & Hodges (2002) Gregory J. Hakim (U. Washington)

  18. Baroclinic Waves & Packets Cyclones & anticyclones often compose waves within larger wave packets. Gregory J. Hakim (U. Washington)

  19. Baroclinic Waves Wavelength ~4000 km Phase speed ~ 15 m/s. Period ~ 3 d. Due to baroclinic instability. Organize into packets. Lim & Wallace (1991) Gregory J. Hakim (U. Washington)

  20. Wave Packet Phase & Group Speed phase speed group speed Chang & Yu (1999) Gregory J. Hakim (U. Washington)

  21. Wave Packet Tracks Jet-stream wave guides. Storm-track recycling. Hakim (2003) Gregory J. Hakim (U. Washington)

  22. Mesoscale Phenomena & Smaller Scales Fronts & frontal waves. Gravity waves. Convection. Shear instabilities. Gregory J. Hakim (U. Washington)

  23. Frontal Waves Paldor et al. (1994) Wakimoto & Bosart (2000) Gregory J. Hakim (U. Washington)

  24. Tropopause Shear Line Instability Gregory J. Hakim (U. Washington)

  25. Tropopause Shear Line Instability Gregory J. Hakim (U. Washington)

  26. Tropopause Shear Line Instability Gregory J. Hakim (U. Washington)

  27. Tropopause Shear Line Instability Gregory J. Hakim (U. Washington)

  28. tropopause Moist Convection Strong vertical mixing Gregory J. Hakim (U. Washington)

  29. Kelvin—Helmholtz Instability Gregory J. Hakim (U. Washington)

  30. Gravity Waves Wavelength ~10 km Gregory J. Hakim (U. Washington)

  31. Gravity Waves Gregory J. Hakim (U. Washington)

  32. How do we better understand cyclones & anticyclones? Need to filter other disturbances from the equations… Gregory J. Hakim (U. Washington)

  33. Ertel Potential Vorticity Gregory J. Hakim (U. Washington)

  34. Vertical Profile of PV • Tropopause • Well-defined as PV jump. • Dynamics focus here. Gregory J. Hakim (U. Washington)

  35. Tropopause Topography (pressure) • High pressure over poles. • Low pressure over tropics. • Strong gradient in mid-latitudes. • Stronger gradient in winter. source: Hoinka (1998) Gregory J. Hakim (U. Washington)

  36. Height-Latitude Tropopause Profile Hoinka (1998) Gregory J. Hakim (U. Washington)

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