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.

Where they occur

What they do

What they look like from spaceGreen dot 60N 180WRed dot: St. Paul Island

Pack ice: Light blueOpen Ocean: Dark BlueSST (monthly mean): RedTrack: BlackBoat: Soviet traulerNWS: St. Paul Island

St. Paul IslandNWS dataTime-Space conversionestimate of central pressure

0Z 7Mar12Z 7Mar0Z 8Mar6Z 8Mar12Z 8Mar18Z 8MarSURFACE

0000 UTC 7 March

Surface850 mb700 mb500 mb

Satellite 2230 UTC 6 Mar

0000 UTC 8 March

Surface700 mb

Satellite 2145 UTC 7 Mar1200 UTC 7 March

Surface700 mb

1200 UTC 8 March

Surface850 mb700 mb500 mb

Satellite 2100 UTC 8 Mar

Landfall1200 UTC 7 March

Surface700 mb

Quasi-Geostrophic Forcing (Q vector formulation)

Quasi-Geostrophic Forcing (Q vector formulation)

Apparent source of energy

Sensible (primary) and latent (secondary) heat flux from warm (in a relative sense) ocean surface.

Sensible HeatFluxes (W/m2)1800 UTCMarch 8, 2005Maximumin region of strong windsin arctic airMinimumin core whereair is warmand winds light

St. Pauls Island at 12Z 7 MarchSt. Pauls Island at 12Z 8 MarchCore of Polar Low21Z 7 March21Z 8 March

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

Model simulation using axisymmetric tropical cyclone model15 vertical layers, 20 km resolution, 1500 km domain

Time evolution of modeled sensible, latent and total heat fluxesSensible heat flux exceeds latent heat flux throughout simulation

Convective heating profiles: vertical redistribution of heatBy the convective scheme used in the modelratio of unresolved (convective parameterization) vs. resolvedLatent heating (precipitation rate).

Temp deviation from model boundaryRelative Humidity

Sensitivity to initial vortex intensity used in the modelConclusion: Polar low will not form unless an initial disturbanceExists, normally associated with baroclinic instability

Sensitivity to sea surface temperature used in the modelConclusion: Final intensity of storm a strong function of SST