ATM S 542 Synoptic Meteorology OverviewOverviewPowerPoint PresentationAtmospheric StructureAtmospheric Energy SpectrumAtmospheric Phenomena by ScaleJet streams & planetary wavesJet StreamsJets: ~ Geostrophic BalanceJet stream vorticityCyclones & AnticyclonesCyclone StructureNorth American CyclonePacific Extratropical CycloneSlide 15Cyclone—Anticyclone Track DensityJet-Level 2.5—6 d VarianceBaroclinic Waves & PacketsBaroclinic WavesWave Packet Phase & Group SpeedWave Packet TracksMesoscale Phenomena & Smaller ScalesFrontal WavesTropopause Shear Line InstabilitySlide 25Slide 26Slide 27Moist ConvectionKelvin—Helmholtz InstabilityGravity WavesSlide 31How do we better understand cyclones & anticyclones?Ertel Potential VorticityVertical Profile of PVTropopause Topography (pressure)Height-Latitude Tropopause ProfileATM S 542 Synoptic Meteorology Overview Gregory J. HakimUniversity of Washington, Seattle, USAwww.atmos.washington.edu/~hakim• Vertical structure of the atmosphere.• Atmospheric phenomena by horizontal scale.• Potential vorticity.• Tropopause.08-21-03 Gregory J. Hakim (U. Washington) 2OverviewAsymptotic 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.08-21-03 Gregory J. Hakim (U. Washington) 3Jets, stirring, organized structures; waves, vortices, convection.08-21-03 Gregory J. Hakim (U. Washington) 4Atmospheric 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.08-21-03 Gregory J. Hakim (U. Washington) 5Atmospheric Energy SpectrumEnergy increases with horizontal length scale.08-21-03 Gregory J. Hakim (U. Washington) 6Atmospheric Phenomena by ScalePlanetary wavesL ~ 10 000 kmH/L ~ .001Ro ~ 0.01CyclonesL ~ 1000 kmH/L ~ .01Ro ~ 0.1Gravity wavesL ~ 10--100 kmH/L ~ .1-1Ro ~ 1ConvectionL ~ 10 kmH/L ~ 1Ro > 1Long, slow Short, fast08-21-03 Gregory J. Hakim (U. Washington) 7Jet streams & planetary waves08-21-03 Gregory J. Hakim (U. Washington) 8Jet Streams08-21-03 Gregory J. Hakim (U. Washington) 9Jets: ~ Geostrophic Balance08-21-03 Gregory J. Hakim (U. Washington) 10Jet stream vorticityWaves & particlesWaves:Information flows through the medium by radiation.Particles (vortices):Information flows through the medium by material transport.08-21-03 Gregory J. Hakim (U. Washington) 11Cyclones & Anticyclones08-21-03 Gregory J. Hakim (U. Washington) 12Cyclone 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.08-21-03 Gregory J. Hakim (U. Washington) 13North American Cyclone08-21-03 Gregory J. Hakim (U. Washington) 14•Intense vortex •Cold air: shallow cellular convection•Warm air: stratiform cloud•Sharp frontal boundariesZoom in on cold front…Pacific Extratropical Cyclone08-21-03 Gregory J. Hakim (U. Washington) 15Scale collapse at cold front: “rope cloud”---narrow line convection.08-21-03 Gregory J. Hakim (U. Washington) 16Cyclone—Anticyclone Track DensityPrimary tracks coincide with time-mean jet stream locations.Hoskins & Hodges (2002)08-21-03 Gregory J. Hakim (U. Washington) 17Jet-Level 2.5—6 d VarianceMaximum variance in storm tracks.Hoskins & Hodges (2002)08-21-03 Gregory J. Hakim (U. Washington) 18Baroclinic Waves & PacketsCyclones & anticyclones often compose waves within larger wave packets.08-21-03 Gregory J. Hakim (U. Washington) 19Baroclinic WavesWavelength ~4000 kmPhase speed ~ 15 m/s.Period ~ 3 d.Due to baroclinic instability.Organize into packets.Lim & Wallace (1991)08-21-03 Gregory J. Hakim (U. Washington) 20Wave Packet Phase & Group Speedphase speedgroup speedChang & Yu (1999)08-21-03 Gregory J. Hakim (U. Washington) 21Wave Packet TracksHakim (2003)Jet-stream wave guides.Storm-track recycling.08-21-03 Gregory J. Hakim (U. Washington) 22Mesoscale Phenomena & Smaller ScalesFronts & frontal waves.Gravity waves.Convection.Shear instabilities.08-21-03 Gregory J. Hakim (U. Washington) 23Frontal WavesWakimoto & Bosart (2000)Paldor et al. (1994)08-21-03 Gregory J. Hakim (U. Washington) 24Tropopause Shear Line Instability08-21-03 Gregory J. Hakim (U. Washington) 25Tropopause Shear Line Instability08-21-03 Gregory J. Hakim (U. Washington) 26Tropopause Shear Line Instability08-21-03 Gregory J. Hakim (U. Washington) 27Tropopause Shear Line Instability08-21-03 Gregory J. Hakim (U. Washington) 28Moist ConvectionStrong vertical mixingtropopause08-21-03 Gregory J. Hakim (U. Washington) 29Kelvin—Helmholtz Instability08-21-03 Gregory J. Hakim (U. Washington) 30Gravity WavesWavelength ~10 km08-21-03 Gregory J. Hakim (U. Washington) 31Gravity Waves08-21-03 Gregory J. Hakim (U. Washington) 32How do we better understand cyclones & anticyclones?Need to filter other disturbances from the equations…08-21-03 Gregory J. Hakim (U. Washington) 33Ertel Potential Vorticity08-21-03 Gregory J. Hakim (U. Washington) 34Vertical Profile of PVTropopause• Well-defined as PV jump.• Dynamics focus here.08-21-03 Gregory J. Hakim (U. Washington) 35Tropopause Topography (pressure)source: Hoinka (1998)• High pressure over poles.• Low pressure over tropics.• Strong gradient in mid-latitudes.• Stronger gradient in winter.08-21-03 Gregory J. Hakim (U. Washington) 36Height-Latitude Tropopause ProfileHoinka