The Coriolis frequency ƒ, also called the Coriolis parameter or Coriolis coefficient,[1] is equal to twice the rotation rate Ω of the Earth multiplied by the sine of the latitude
The rotation rate of the Earth (Ω = 7.2921 × 10−5 rad/s) can be calculated as 2π / T radians per second, where T is the rotation period of the Earth which is one sidereal day (23 h 56 min 4.1 s).
Inertial oscillations on the surface of the Earth have this frequency.
Consider a body (for example a fixed volume of atmosphere) moving along at a given latitude
), however, is perpendicular to the plane containing both the earth's angular velocity vector
) and the body's own velocity in the rotating reference frame
The local horizontal direction of the Coriolis force is thus
This force acts to move the body along longitudes or in the meridional directions.
is the radius of curvature of the path of object (defined by
is the magnitude of the spin rate of the Earth, to obtain Thus the Coriolis parameter,
, is the angular velocity or frequency required to maintain a body at a fixed circle of latitude or zonal region.
If the Coriolis parameter is large, the effect of the Earth's rotation on the body is significant since it will need a larger angular frequency to stay in equilibrium with the Coriolis forces.
Alternatively, if the Coriolis parameter is small, the effect of the Earth's rotation is small since only a small fraction of the centripetal force on the body is canceled by the Coriolis force.
strongly affects the relevant dynamics contributing to the body's motion.
These considerations are captured in the nondimensionalized Rossby number.
This parameter becomes important, for example, in calculations involving Rossby waves.