The Coriolis Force and the Weather
Of the natural phenomena affected by the Coriolis force the one we
are most aware of is the system of winds and weather patterns on the Earth.
Because air can
move relatively quickly and over great distances, the effect here too
is cumulative. Large weather systems represent a relatively steady state
of air flowing in an
approximately fixed direction, which implies there is almost no acceleration
of any air mass.
This in turn implies a balance of the major forces which are:
The Coriolis force tending to deflect air to the right when viewed
in the direction of the wind and,
The pressure force tending to drive the air from regions of high to
The result can summarized by the geostrophic wind formula v =
1/(2rwe' ) (dP/dH)
where r is the density of air and dH
the horizontal separation of isobars of pressure difference dP.
For example, a common occurrence in the winter is a great region of high
pressure over the cold North American continent, and a region of low pressure
over the warmer North Atlantic in the region of Greenland. If the pressure
in Chicago is say, 101.5 kP, and in Quebec City 101.0 kP, then we can expect
a steady wind at 10 km/hr from the northwest as shown in Fig. 3.
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