In meteorology, the balance between the "Coriolis force" and the horizontal pressure gradient that determines the first-order circulation patterns of the open ocean: The condition of geostrophy can be exemplified by the Coriolis force that is an apparent force exerted on a moving object by the rotation of the Earth. This object moves horizontally above the Earth's surface in the Northern Hemisphere and tends to show a rightward deflection, and one in the Southern Hemisphere tends to show a leftward deflection.

The situation of geostrophy was described by Gaspard de Coriolis (1792-1843) who was a French civil engineer.