Geostrophic balance

Summary

Geostrophic balance is the balance between the Coriolis force and the horizontal pressure gradient force in a rotating fluid. It holds approximately for large-scale, slow flows in the atmosphere and the ocean, where the Rossby number is small. The flow it gives, the geostrophic flow, runs along the isobars instead of across them. It is the leading-order balance of geophysical fluid dynamics and the starting point of the quasi-geostrophic equations.