ATM S 542 Synoptic Meteorology Overview Gregory J. Hakim University of Washington, Seattle, USA www.atmos.washington.edu/~hakim Vertical structure of the.

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Presentation transcript:

ATM S 542 Synoptic Meteorology Overview Gregory J. Hakim University of Washington, Seattle, USA Vertical structure of the atmosphere. Atmospheric phenomena by horizontal scale. Potential vorticity. Tropopause.

Gregory J. Hakim (U. Washington)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 H 2 O 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 Atmospheric Phenomena by Scale Planetary waves L ~ km H/L ~.001 Ro ~ 0.01 Cyclones L ~ 1000 km H/L ~.01 Ro ~ 0.1 Gravity waves L ~ km H/L ~.1-1 Ro ~ 1 Convection L ~ 10 km H/L ~ 1 Ro > 1 Long, slowShort, 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 Intense vortex Cold air: shallow cellular convection Warm air: stratiform cloud Sharp frontal boundaries Zoom in on cold front… Pacific Extratropical Cyclone

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 Primary tracks coincide with time-mean jet stream locations. Hoskins & Hodges (2002)

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 Hakim (2003) Jet-stream wave guides. Storm-track recycling.

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 Wakimoto & Bosart (2000)Paldor et al. (1994)

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 Moist Convection Strong vertical mixing tropopause

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) source: Hoinka (1998) High pressure over poles. Low pressure over tropics. Strong gradient in mid-latitudes. Stronger gradient in winter.

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