# Potential vorticity

Potential vorticity (PV) is a quantity which is proportional to the dot product of vorticity and stratification that, following a parcel of air or water, can only be changed by diabatic or frictional processes. It is a useful concept for understanding the generation of vorticity in cyclogenesis (the birth and development of a cyclone), especially along the polar front, and in analyzing flow in the ocean.

It is also useful in tracing intrusions of stratospheric air deep into the troposphere in the vicinity of jet streaks, a concentrated region within a jet stream where the wind speeds are the strongest. It acts as a flow tracer in the ocean as well. It can also be used to explain how a range of mountains like the Andes can make the upper westerly winds swerve towards the equator and back.

Baroclinic instability requires the presence of a potential vorticity gradient along which waves amplify during cyclogenesis.

PV conservation

Mathematically, one form of potential vorticity is given by the equation:

$\left\{ m PV\right\} = frac\left\{1\right\}\left\{ ho\right\},zeta,. abla heta$
where $ho$ is the fluid density, $zeta$ is the absolute vorticity and $abla heta$ is the gradient of the potential temperature. It can be shown through a combination of the first law of thermodynamics and momentum conservation that potential vorticity can only be changed by diabatic heating (such as latent heat released from condensation) or frictional processes. This conservation is the atmospheric equivalent to inertia. A spinning ice skater with her arms spread out laterally can accelerate her rate of spin by contracting her arms. Similarly, when a vortex of air is broad, it is in turn, slow. When the air converges, to maintain potential vorticity, the air speed increases, resulting in a stretched rince vortex. Divergence causes the vortex to spread, slowing down the rate of spin.

ee also

* Vorticity

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• potential vorticity — noun a quantity which is proportional to the product of vorticity and stratification. When applied to air parcels, aids the understanding of cyclogenesis …   Wiktionary

• Vorticity — is a mathematical concept used in fluid dynamics. It can be related to the amount of circulation or rotation (or more strictly, the local angular rate of rotation) in a fluid.Clancy, L.J., Aerodynamics , Section 7.11] The average vorticity zeta… …   Wikipedia

• Potential flow — streamlines around a NACA 0012 airfoil at 11° angle of attack, with upper and lower streamtubes identified. In fluid dynamics, potential flow describes the velocity field as the gradient of a scalar function: the velocity potential. As a result,… …   Wikipedia

• Convective available potential energy — A skew T plot showing a morning sounding with a large hydrolapse followed by an afternoon sounding showing the cooling which occurred in the mid levels resulting in an unstable atmosphere as surface parcels have now become negatively buoyant. The …   Wikipedia

• PVU — Potential Vorticity Unit (Miscellaneous » Unit Measures) * Paleoenvironmental data (PaleoVu) (Computing » File Extensions) * Portable Verification Unit (Medical » Physiology) * Portable Verification Unit (Governmental » Military) * Portable… …   Abbreviations dictionary

• Convection — This figure shows a calculation for thermal convection in the Earth s mantle. Colors closer to red are hot areas and colors closer to blue are cold areas. A hot, less dense lower boundary layer sends plumes of hot material upwards, and likewise,… …   Wikipedia

• Eyewall replacement cycle — Concentric eyewalls seen in Hurricane Katrina as it travels west through the Gulf of Mexico. Eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than… …   Wikipedia

• PVU — In meteorology, the potential vorticity unit (PVU) is defined as 10 6 K m2 kg 1 s 1.In adiabatic, frictionless flow, potential vorticity is the product of absolute vorticity and static stability on a constant potential temperature surface.ee… …   Wikipedia

• Breaking wave — In physics, a breaking wave is a wave whose amplitude reaches a critical level at which some process can suddenly start to occur that causes large amounts of wave energy to be dissipated. At this point, simple physical models describing the… …   Wikipedia

• Potentielle Vortizität — Die potentielle Vortizität oder potentielle Vorticity ist ein Maß für die Scherung von Strömungen und ist insbesondere in der Ozeanographie und der Meteorologie von Bedeutung. Sie kombiniert die Erhaltung der Vortizität mit der Erhaltung der… …   Deutsch Wikipedia