1 / 91

A Potpourri of Interesting Research Problems

A Potpourri of Interesting Research Problems. TC Effects on El Nino?.

corbin
Download Presentation

A Potpourri of Interesting Research Problems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Potpourri of Interesting Research Problems

  2. TC Effects on El Nino? This plot shows a measure of El Niño/La Niña (green) and a measure of the power put into the far western Pacific Ocean by tropical cyclones (blue). The blue curve has been shifted rightward by two years on this graph. There is the suggestion that powerful cyclones in the western Pacific can trigger El Niño/La Niña cycles.

  3. Agukabams(aka Landphoons, Terracanes)From aboriginal roots “agu” (land) and “kabam” (storm) • Case studies • Hypothesis • Simple model Emanuel, K., J. Callaghan, and P. Otto, 2008: A hypothesis for the re-development of warm-core cyclones over northern Australia. Mon. Wea. Rev., 136, 3863-3872

  4. Case : TC Abigail, Feb-March, 2001

  5. Best-track winds

  6. Hypothesis: Non-baroclinic rejuvenation of tropical cyclones over land can be caused by rapid flux of heat out of hot, sandy soils that have been moistened by the early rains of the system

  7. 20 cm Soil Temp at Halls Creek during Passage of Abigail

  8. Idealized Experiments: Constant translation velocity and environmental temperature,initialization with a warm core vortex with maximum winds of 17 ms-1

  9. Sensitivity to Initial Soil Temperature(translation speed = 13 km hr-1)

  10. Sensitivity to thermal diffusivity

  11. Sensitivity to translation speed

  12. Effect of depletion of water: PBL environmental RH declines from 80% to 0% over 8 days

  13. Abigail Hindcast

  14. Tropical Storm Erin, 2007

  15. But then, deep in the heart of Oklahoma....

  16. 12 GMT August 18 2007

  17. 18 GMT August 18 2007

  18. 00 GMT August 19 2007

  19. 06 GMT August 19 2007

  20. 12 GMT August 19 2007

  21. Oklahoma Soils

  22. Soil temperature record at Hinton, OK

  23. Estimate of Soil Heat Flux

  24. Hurricanes in the Persian Gulf? Annual Frequency=0.04

  25. Back to Norway A Return to the Concept of Air Masses

  26. Two Key Concepts from the Norwegian School: • Fronts • Air masses Bergeron, 1922: An air mass is a vast body of air whose physical properties are more or less uniform in the horizontal, while abrupt changes are found along its boundaries, i.e. the frontal zones.

  27. Bjerknes and Solberg, 1922 “The cyclone consists of two essentially different air-masses, the one of cold and the other of warm origin. They are separated by a fairly distinct boundary surface which runs through the center of the cyclone. This boundary surface is imagined to continue, more or less distinctly, through the greater part of the troposphere.” [Emphasis mine]

  28. Early Emphasis on Air Mass Formation Bergeron, 1922, visualized air masses as forming within semi-permanent circulation systems, such as wintertime continental highs and subtropical anticyclones; “The air that takes part in the circulation around any such system will become subject to the prolonged influences of the underlying surface, with the result that there will be a tendency for distinct properties to be acquired. “Although the vertical structure of any air mass may be modified by differential advection and vertical stretching and shrinking, the more direct modifications are brought about by interactions between the atmosphere and the earth’s surface.” [Bergeron, as paraphrased by Petterssen, 1954]

  29. Sanders, 1955:“The intense surface frontal zone attains maximum strength near the ground and weakens rapidly with altitude.”

  30. The Dynamics Revolution Carl-Gustav Rossby and Hans Ertel: Conservation and invertibility of potential vorticity: is the fluid velocity, is the fluid density, and S is any conserved state variable (usually the entropy)

  31. Rossby Waves: • Wherever there are gradients of q on surfaces of constant s • Wherever there are gradients of s on rigid boundaries

  32. Baroclinic Instability and Fronts • Eady’s 1949 model of baroclinic instability: No interior gradients of potential vorticity • Hoskins and Bretherton’s 1972 semi-geostrophic model of frontogenesis: no interior gradients of PV; fronts develop only at surface and tropopause

  33. Contemporary View: • PV dynamics seated mostly in surface and tropopause entropy gradients • Troposphere proper can be approximated as a fluid of constant PV or constant PV gradient (β) • 5-10 day forecast errors owing to dynamical error growth; sensitivity can be measured by adiabatic error growth • Fronts are features of surface and (deformed) tropopause

  34. What Ever Happened to Thermodynamics?

  35. Some basic principles • Heating of cold air masses from below is a relatively rapid process, occurring usually in a few days • Cooling of air masses from below may require many tens of days

  36. Successive temperature soundings at Fairbanks, Alaska, in December, 1961. Curves labeled with time in days relative to first sounding.

More Related