Potential vorticity

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The potential vorticity or potential vorticity is important as a measure of the shear of currents, especially in oceanography and meteorology . It combines the conservation of vorticity  (vorticity) with the conservation of mass and is a special case of ertel rule vortex set .

The potential vorticity is defined as:

With

  • the relative vorticity
  • the planetary vorticity
  • the density
  • the Nabla operator
  • a scalar quantity that only depends on the pressure and the density, for example the potential temperature or the potential density .

The PVU ( potential vorticity unit ) is commonly used in meteorology as the unit of measurement for potential vorticity :

The source or sink of potential vorticity are baroclinic effects and friction .

If the following restrictions apply to the flow:

  1. no friction
  2. is the conservation quantity , d. H.
  3. Barotropy , d. H. or

then the potential vorticity is also a conserved quantity:

It follows that the relative vorticity must decrease as the planetary vorticity increases, e.g. B. when moving a column of water to the north. This is analogous to the conservation of angular momentum in mechanics.

When is a function of density and pressure, i. H. , this is synonymous with adiabasia . Then the obtained potential vorticity can also be represented as:

With

literature

Web link

  • Michael E. McIntyre: Potential vorticity ( PDF )