polar lows: so-called “hurricanes” of the arctic
DESCRIPTION
Polar lows: So-called “Hurricanes” of the Arctic. Key papers: Emanuel and Rotunno: Polar lows as Arctic Hurricanes Tellus, 41A, 1-17 Businger: Arctic Hurricanes, American Scientist, Jan 91 Businger and Baik: An arctic hurricane over the Bering Sea - PowerPoint PPT PresentationTRANSCRIPT
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Polar lows: So-called Hurricanes of the ArcticKey papers: Emanuel and Rotunno: Polar lows as Arctic Hurricanes Tellus, 41A, 1-17 Businger: Arctic Hurricanes, American Scientist, Jan 91 Businger and Baik: An arctic hurricane over the Bering Sea MWR, 119, 2293.
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Where they occur
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What they do
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What they look like from spaceGreen dot 60N 180WRed dot: St. Paul Island
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Pack ice: Light blueOpen Ocean: Dark BlueSST (monthly mean): RedTrack: BlackBoat: Soviet traulerNWS: St. Paul Island
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St. Paul IslandNWS dataTime-Space conversionestimate of central pressure
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0Z 7Mar12Z 7Mar0Z 8Mar6Z 8Mar12Z 8Mar18Z 8MarSURFACE
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0000 UTC 7 March
Surface850 mb700 mb500 mb
Satellite 2230 UTC 6 Mar
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0000 UTC 8 March
Surface700 mb
Satellite 2145 UTC 7 Mar1200 UTC 7 March
Surface700 mb
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1200 UTC 8 March
Surface850 mb700 mb500 mb
Satellite 2100 UTC 8 Mar
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Landfall1200 UTC 7 March
Surface700 mb
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Quasi-Geostrophic Forcing (Q vector formulation)
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Quasi-Geostrophic Forcing (Q vector formulation)
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Apparent source of energy
Sensible (primary) and latent (secondary) heat flux from warm (in a relative sense) ocean surface.
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Sensible HeatFluxes (W/m2)1800 UTCMarch 8, 2005Maximumin region of strong windsin arctic airMinimumin core whereair is warmand winds light
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St. Pauls Island at 12Z 7 MarchSt. Pauls Island at 12Z 8 MarchCore of Polar Low21Z 7 March21Z 8 March
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Potential Thickness vs Environmental Thickness (m)Potential thickness: Thickness (1000-500 mb) that would result if the environmental lapse rate were modified to lie along a moist adiabat representing saturation at 1000 mb at the sea surface temperature.Upper limit to which sea surface can modify atmosphere
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Model simulation using axisymmetric tropical cyclone model15 vertical layers, 20 km resolution, 1500 km domain
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Time evolution of modeled sensible, latent and total heat fluxesSensible heat flux exceeds latent heat flux throughout simulation
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Convective heating profiles: vertical redistribution of heatBy the convective scheme used in the modelratio of unresolved (convective parameterization) vs. resolvedLatent heating (precipitation rate).
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Temp deviation from model boundaryRelative Humidity
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Sensitivity to initial vortex intensity used in the modelConclusion: Polar low will not form unless an initial disturbanceExists, normally associated with baroclinic instability
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Sensitivity to sea surface temperature used in the modelConclusion: Final intensity of storm a strong function of SST