rotate under the baseball (or parcel of air). Although the baseball continues moving
north relative to our geostationary point of view, when the path of the baseball (or air
parcel) is traced on the Earth’s surface, it appears to have curved to the right. The
apparent force which accounts for such curved motion in a rotating frame of reference
is called the Coriolis effect. The Coriolis effect accounts for the large scale horizontal
winds that are driven by the general circulation of the atmosphere.
The influence of the Coriolis effect on general circulation gives us the prevailing wind
regimes that were observed by sailors centuries ago. For example, the winds that
move from north to south from the lower latitudes into the ITCZ are deflected to the
right (westward) and produce the northeast trade winds, observed in the Caribbean
and Hawaii (figure 10, page 22). The winds that move south-to-north in the midlati-
tudes are deflected to the right and form the prevailing westerlies in this area.
figure 9.The Coriolis effect has several important characteristics.- The Coriolis effect is a deflecting force. It acts at right angles to wind direc-
tion but does not affect wind speed. - The strength of the Coriolis effect is proportional to wind speed.
- The Coriolis effect deflects winds to the right in the Northern Hemisphere.
Thus northerly moving winds are bent eastward and southerly moving
winds are bent westward. The reverse is true in the Southern Hemisphere
(winds are deflected to the left, meaning northerly moving winds are bent
westward and southerly moving winds are bent eastward.) - There is no effect at the equator.