In the atmospheric sciences, vorticity is a property that characterizes largescale rotation of air masses in currents with a roughly vertical axis of rotation, such as cyclones or tornadoes.
Relative and absolute vorticity are defined as the zcomponents of the curls of relative (i.e., in relation to Earth's surface) and absolute wind velocity, respectively.
This gives
for relative vorticity and
for absolute vorticity, where u and v are the zonal (x direction) and meridional (y direction) components of wind velocity.
The barotropic vorticity equation is the simplest way for forecasting the movement of Rossby waves[?] (that is, the troughs[?] and ridges[?] of 500 mb geopotential) over a limited amount of time (a few days). In the 1950s, the first successful programs for numerical weather forecasting[?] thus utilized that equation.
In modern numerical weather forecasting models and GCMs, vorticity is just one of many prognostic variables.
Vorticity is important in many other areas of fluid dynamics. For instance, the lift distribution over a finite wing may be approximated by assuming that each segment of the wing has a semiinfinite trailing vortex behind it. It is then possible to solve for the strength of the vortices using the criterion that there be no flow induced through the surface of the wing.
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