Rossby Number
D1. Physical and chemical oceanography and marine meteorologyDefinition
Ratio of inertial to Coriolis forces.
The Rossby number Ro = U/(f L) compares the inertial (advective) acceleration to the Coriolis acceleration, where U and L are velocity and length scales and f is the Coriolis parameter. When Ro is small (large scales, slow flow) rotation dominates and the flow is nearly geostrophic; when Ro is of order one or larger (small eddies, the equator, fronts) inertial effects matter. It is the master scaling parameter of rotating fluid dynamics.