where f is the Coriolis parameter 2 Ω Ω sin ⁡ ⁡ φ φ , introduced above (where φ φ is the latitude). The time taken for the mass to complete a full circle is therefore 2 π π / f . The Coriolis parameter typically has a mid-latitude value of about 10 s ; hence for a typical atmospheric speed of 10 m/s (22 mph), the radius is 100 km (62 mi) with a period of about 17 hours. For an ocean current with a typical speed of 10 cm/s (0.22 mph), the radius of an inertial circle is 1 km (0.6 mi). These inertial circles are clockwise in the northern hemisphere (where trajectories are bent to the right) and anticlockwise in the southern hemisphere.