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Supercells

Supercells. MICRO-. PHYSICS. Physical processes controlling cell types:. Buoyancy processes: basic updraft/downdraft, (ordinary cells) Gust front processes : triggering of new cells, upscale growth, (multicells)

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Supercells

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  1. Supercells

  2. MICRO- PHYSICS

  3. Physical processes controlling cell types: • Buoyancy processes: basic updraft/downdraft, (ordinary cells) • Gust front processes: triggering of new cells, upscale growth, (multicells) • Dynamic processes: rotating updraft, dynamic vertical pressure gradient forcing, (supercells)

  4. Physical processes controlling cell types: • Buoyancy processes: basic updraft/downdraft, (ordinary cells) • Gust front processes: triggering of new cells, upscale growth, (multicells) • Dynamic processes: rotating updraft, dynamic vertical pressure gradient forcing, (supercells)

  5. Momentum Eq. Dynamic Pressure Eq. --

  6. Linearise pressure eq. about U(z), V(z) (environmental vertical wind shear) So, since

  7. 2D Updraft in Sheared Environment:

  8. Vorticity Equation: Vertical Vorticity: tilting stretching

  9. Vortex Tube Circulation:

  10. Theorems for inviscid fluids with conservative external forces (e.g., no baroclinicity, buoyancy) (Helmholtz, 1858) ….Vortex lines (tubes) are material lines that are frozen into the fluid. ….The circulation (strength) of a vortex tube is invariant …The circulation on any curve around a vortex tube is constant along the tube.

  11. Tilting: Linearized about a mean vertical wind shear:

  12. Vertical Momentum Eq. (rewritten) (dynamic) + (buoyancy)

  13. (H = horizontal shearing deformation) So, for a wind profile in pure rotation: So, again, since

  14. Supercell Hodographs: Supercell processes are Galilean invariant!!!

  15. Linearise pressure eq. about U(z), V(z) (environmental vertical wind shear) So, since

  16. Bunkers et al. WAF 2000

  17. Weisman and Rotunno, Jas 2000

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