Beta plane

In geophysical fluid dynamics, an approximation whereby the Coriolis parameter, f, is set to vary linearly in space is called a beta plane approximation. On a rotating sphere such as the earth, f varies with the sine of latitude; a linear approximation to this variability about a given latitude (in the sense of a Taylor series expansion) can be visualized as a tangent plane touching the surface of the sphere at this latitude. The relevant dynamics can then be cast in a planar, Cartesian coordinate system rather than a spherical one. The name 'beta plane' derives from the convention to denote the linear coefficient of variation with the Greek letter β.