Okubo–Weiss parameter

In fluid mechanics, the Okubo–Weiss parameter, is a measure of the relative importance of deformation and rotation at a given point. It is calculated as the sum of the squares of normal and shear strain minus the relative vorticity. This is widely applicable in fluid properties particularly in identifying and describing oceanic eddies.
For a horizontally non-divergent flow in the ocean, the parameter is given by:
where:

OW is widely used in the fields of Meteorology and Oceanography to identify regions of strong vorticity within atmospheric and oceanic flows. It is often employed as a tracer for cyclonic development because it is generally less "noisy" than relative vorticity alone. The Okubo-Weiss parameter quantifies the balance between rotational and deformational components of the flow: positive values indicate that deformation dominated, while negative values indicate that rotation is dominant.