1. 10/25/2006 13th Cyclone Workshop1 Analysis of the potential vorticity budget of a tropopause polar cyclone Steven M. Cavallo and Gregory J. Hakim University of Washington Department of Atmospheric Sciences

2. 10/25/2006 13th Cyclone Workshop2 Outline Tropopause polar vortices (TPVs) Ertel potential vorticity (EPV) Tropopause maps November 2005 TPV PV budget of November 2005 TPV

3. 10/25/2006 13th Cyclone Workshop3 Waves and vortices Vortex Wave Consider a materially conserved field such as potential vorticity (PV):  Linear solutions are waves, nonlinear are vortices Observations tell us that upper level disturbances are more wave-like near jet stream and vortex-like away from jet stream

4. 10/25/2006 13th Cyclone Workshop4 Waves and vortices Closed contours in a materially conserved field:  Fluid parcels are bound by closed contours of that field Using potential vorticity (PV), changes in vortex strength can be assessed by changes in fluid properties within these closed contours These vortices often drift into mid-latitudes, sometimes triggering surface cyclogenesis

5. 10/25/2006 13th Cyclone Workshop5 Tropopause polar vortices (TPVs) Tropopause polar vortices (TPVs) are: Vortices that occur well poleward of the jet stream Based on the tropopause Cold core Although there is considerable understanding about the life cycles of surface extratropical cyclones, relatively less is known about the upper-level disturbances governing them

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7. 10/25/2006 13th Cyclone Workshop7 Radiational cooling at cloud top Radiational heating at cloud base

8. 10/25/2006 13th Cyclone Workshop8 Heating ProfileEPV Changes

9. 10/25/2006 13th Cyclone Workshop9 Heating ProfileEPV Changes

10. 10/25/2006 13th Cyclone Workshop10 Potential Vorticity & Isentropic Surfaces PV surfaces (black) in PVU, isentropic surfaces (red) in Kelvin 1 PVU = potential vorticity unit = m 2 K kg -1 s -1 (Adapted from Hoskins 1990)

11. 10/25/2006 13th Cyclone Workshop11 November 2005 TPV GFS analysis tropopause pressureCoral Harbour, NT sounding 21 November 2005 at 00 UTC

12. 10/25/2006 13th Cyclone Workshop12 November 2005 TPV GFS analysis tropopause pressureCoral Harbour, NT sounding 22 November 2005 at 00 UTC

13. 10/25/2006 13th Cyclone Workshop13 November 2005 TPV GFS analysis tropopause pressureCoral Harbour, NT sounding 23 November 2005 at 00 UTC

14. 10/25/2006 13th Cyclone Workshop14 November 2005 TPV GFS analysis tropopause pressureCoral Harbour, NT sounding 24 November 2005 at 00 UTC

15. 10/25/2006 13th Cyclone Workshop15 November 2005 TPV Horizontal grid spacing 30 km, 31 vertical levels 5-class microphysics, RRTM longwave radiation GFS analysis and boundaries updated every three hours WRF simulations:

16. 10/25/2006 13th Cyclone Workshop16 Siberia Averages within 285 K closed contour

17. 10/25/2006 13th Cyclone Workshop17 Siberia Averages within 285 K closed contour

18. 10/25/2006 13th Cyclone Workshop18 Siberia Averages within 285 K closed contour

19. 10/25/2006 13th Cyclone Workshop19 Hudson Bay Averages within 280 K closed contour

20. 10/25/2006 13th Cyclone Workshop20 Hudson Bay Values at center of vortex

21. 10/25/2006 13th Cyclone Workshop21 Siberia EPV terms Diabatic components

22. 10/25/2006 13th Cyclone Workshop22 Hudson Bay EPV terms Diabatic components

23. 10/25/2006 13th Cyclone Workshop23 Summary TPV strengthening from cloud-top radiational cooling TPV weakening processes not as clear, but weakening appears to occur when latent heating effects dominate the radiational effects What is the contribution of the frictional component? To what degree is implicit model diffusion effecting the budget closure?

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