Page 255 - PPL-engelsk 2025
P. 255
Meteorology
3.4.3.3 Pressure Gradient Force
Why does the wind not blow directly from high to low pressure?
Here we see two pressure systems.
On the left, a weak system with a relatively low pressure drop per unit distance.
The pressure gradient is relatively weak, and the wind will also be weak.
The system on the right is a stronger low pressure, and the distance between
the isobars is smaller. This means the pressure change per unit distance is
greater, resulting in stronger winds.
We will now explain why the wind's direction is not directly from low to high
pressure.
We've discussed this before. It is due to the Coriolis force.
In the figure here, you can see the "apparent"
deflection of an air mass (1 and 2), which
moves in a northerly direction.
The three red arrows indicate the movement
of objects pinned to the Earth.
The Earth's rotational speed is greatest at the
equator.
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 255
