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Meteorology
When moving air from the equator to the north, it retains its rotational speed
(about 1600 km/h), but since the Earth's circumference decreases as you move
away from the equator, from Earth's perspective, it seems that the air changes
direction and deflects slightly to the right.
Conversely, in the Southern Hemisphere, from Earth's perspective, the wind
appears to turn to the left.
See an animation here.
The illustration below shows how the wind is deflected to the right and, as we
approach low pressure, ends up being parallel to the isobars.
Wind arises when a pressure gradient force sets air in motion (bottom left).
At first, the Coriolis force is small, but as the wind grows stronger, the Coriolis
force also increases.
When the two forces—Coriolis and pressure gradient—are equal and opposite,
the wind will blow parallel to the isobars (and to the left of a low pressure).
The wind blowing parallel to the isobars is the geostrophic wind.
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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 256
