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.

Gregory J. Hakim (U. Washington) 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. 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Jets, stirring, organized structures; waves, vortices, convection. 08-21-03 Gregory J. Hakim (U. Washington)

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. 12:03 UTC, 25 kts sustained winds, gusting to 35 kts (125 knots = 144 mph) (1 knot = 1.15 mph) 08-21-03 Gregory J. Hakim (U. Washington)

Atmospheric Energy Spectrum Energy increases with horizontal length scale. 08-21-03 Gregory J. Hakim (U. Washington)

Atmospheric Phenomena by Scale 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 Long, slow Short, fast 08-21-03 Gregory J. Hakim (U. Washington)

Jet streams & planetary waves 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Jet Streams 08-21-03 Gregory J. Hakim (U. Washington)

Jets: ~ Geostrophic Balance 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Jet stream vorticity Waves & particles Waves: 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)

Cyclones & Anticyclones 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) 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. 08-21-03 Gregory J. Hakim (U. Washington)

North American Cyclone 08-21-03 Gregory J. Hakim (U. Washington)

Pacific Extratropical Cyclone Intense vortex Cold air: shallow cellular convection Warm air: stratiform cloud Sharp frontal boundaries L Zoom in on cold front… 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Scale collapse at cold front: “rope cloud”---narrow line convection. 08-21-03 Gregory J. Hakim (U. Washington)

Cyclone—Anticyclone Track Density Hoskins & Hodges (2002) Primary tracks coincide with time-mean jet stream locations. 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Jet-Level 2.5—6 d Variance Maximum variance in storm tracks. Hoskins & Hodges (2002) 08-21-03 Gregory J. Hakim (U. Washington)

Baroclinic Waves & Packets Cyclones & anticyclones often compose waves within larger wave packets. 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Baroclinic Waves Wavelength ~4000 km Phase 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)

Wave Packet Phase & Group Speed phase speed group speed Chang & Yu (1999) 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Wave Packet Tracks Jet-stream wave guides. Storm-track recycling. Hakim (2003) 08-21-03 Gregory J. Hakim (U. Washington)

Mesoscale Phenomena & Smaller Scales Fronts & frontal waves. Gravity waves. Convection. Shear instabilities. 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Frontal Waves Paldor et al. (1994) Wakimoto & Bosart (2000) 08-21-03 Gregory J. Hakim (U. Washington)

Tropopause Shear Line Instability 08-21-03 Gregory J. Hakim (U. Washington)

Tropopause Shear Line Instability 08-21-03 Gregory J. Hakim (U. Washington)

Tropopause Shear Line Instability 08-21-03 Gregory J. Hakim (U. Washington)

Tropopause Shear Line Instability 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Moist Convection tropopause Strong vertical mixing 08-21-03 Gregory J. Hakim (U. Washington)

Kelvin—Helmholtz Instability 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Gravity Waves Wavelength ~10 km 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Gravity Waves 08-21-03 Gregory J. Hakim (U. Washington)

How do we better understand cyclones & anticyclones? Need to filter other disturbances from the equations… 08-21-03 Gregory J. Hakim (U. Washington)

Ertel Potential Vorticity 08-21-03 Gregory J. Hakim (U. Washington)

Gregory J. Hakim (U. Washington) Vertical Profile of PV Tropopause Well-defined as PV jump. Dynamics focus here. 08-21-03 Gregory J. Hakim (U. Washington)

Tropopause Topography (pressure) High pressure over poles. Low pressure over tropics. Strong gradient in mid-latitudes. Stronger gradient in winter. source: Hoinka (1998) 08-21-03 Gregory J. Hakim (U. Washington)

Height-Latitude Tropopause Profile Hoinka (1998) 08-21-03 Gregory J. Hakim (U. Washington)