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Polar lows: So-called “Hurricanes” of the Arctic

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

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Polar lows: So-called “Hurricanes” of the Arctic

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  1. 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 MWR, 119, 2293.

  2. Where they occur…

  3. What they do…

  4. What they look like from space… Green dot 60N 180W Red dot: St. Paul Island

  5. Pack ice: Light blue Open Ocean: Dark Blue SST (monthly mean): Red Track: Black Boat: Soviet trauler NWS: St. Paul Island

  6. St. Paul Island NWS data Time-Space conversion estimate of central pressure

  7. 0Z 7Mar 12Z 7Mar 0Z 8Mar SURFACE 6Z 8Mar 12Z 8Mar 18Z 8Mar

  8. 0000 UTC 7 March Surface 850 mb 700 mb 500 mb Satellite 2230 UTC 6 Mar

  9. 1200 UTC 7 March Surface 700 mb 0000 UTC 8 March Surface 700 mb Satellite 2145 UTC 7 Mar

  10. 1200 UTC 8 March Surface 850 mb 700 mb 500 mb Satellite 2100 UTC 8 Mar

  11. 1200 UTC 7 March Surface 700 mb Landfall

  12. Quasi-Geostrophic Forcing (Q vector formulation)

  13. Quasi-Geostrophic Forcing (Q vector formulation)

  14. Apparent source of energy… Sensible (primary) and latent (secondary) heat flux from “warm” (in a relative sense) ocean surface.

  15. Sensible Heat Fluxes (W/m2) 1800 UTC March 8, 2005 Maximum in region of strong winds in arctic air Minimum in core where air is warm and winds light

  16. Core of Polar Low St. Paul’s Island at 12Z 7 March St. Paul’s Island at 12Z 8 March 21Z 7 March 21Z 8 March

  17. “Potential Thickness” vs Environmental Thickness (m) Upper limit to which sea surface can modify atmosphere 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.

  18. Model simulation using axisymmetric tropical cyclone model 15 vertical layers, 20 km resolution, 1500 km domain

  19. Time evolution of modeled sensible, latent and total heat fluxes Sensible heat flux exceeds latent heat flux throughout simulation

  20. Convective heating profiles: vertical redistribution of heat By the convective scheme used in the model ratio of unresolved (convective parameterization) vs. resolved Latent heating (precipitation rate).

  21. Temp deviation from model boundary Relative Humidity

  22. Sensitivity to initial vortex intensity used in the model Conclusion: Polar low will not form unless an initial disturbance Exists, normally associated with baroclinic instability

  23. Sensitivity to sea surface temperature used in the model Conclusion: Final intensity of storm a strong function of SST

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