Editing Coriolis force (section)

====Inertial circles====
An air or water mass moving with speed <math>v\,</math> subject only to the Coriolis force travels in a circular trajectory called an ''inertial circle''. Since the force is directed at right angles to the motion of the particle, it moves with a constant speed around a circle whose radius <math>R</math> is given by:
<math display="block">R = \frac{v}{f}</math>
where <math>f</math> is the Coriolis parameter <math>2 \Omega \sin \varphi</math>, introduced above (where <math>\varphi</math> is the latitude). The time taken for the mass to complete a full circle is therefore <math>2\pi/f</math>. The Coriolis parameter typically has a mid-latitude value of about 10<sup>−4</sup>&nbsp;s<sup>−1</sup>; hence for a typical atmospheric speed of {{convert|10|m/s|mph|sp=us|abbr=on}}, the radius is {{convert|100|km|0|sp=us|abbr=on}} with a period of about 17&nbsp;hours. For an ocean current with a typical speed of {{convert|10|cm/s|mph|sp=us|abbr=on}}, the radius of an inertial circle is {{convert|1|km|1|sp=us|abbr=on}}. These inertial circles are clockwise in the northern hemisphere (where trajectories are bent to the right) and anticlockwise in the southern hemisphere.

If the rotating system is a parabolic turntable, then <math>f</math> is constant and the trajectories are exact circles. On a rotating planet, <math>f</math> varies with latitude and the paths of particles do not form exact circles. Since the parameter <math>f</math> varies as the sine of the latitude, the radius of the oscillations associated with a given speed are smallest at the poles (latitude of ±90°), and increase toward the equator.<ref name=Marshall2>{{Cite book|title= Atmosphere, Ocean and Climate Dynamics: An Introductory Text | page = 98 |author1=Marshall, John|author2=Plumb, R. Alan |url=https://books.google.com/books?id=aTGYbmVaA_gC&pg=PA98 |isbn=9780125586917 |year=2007 |publisher=Elsevier Academic Press |location=Amsterdam}}</ref>