Adiabatic flow and Catabatic flow
In response to a student who asks us what happens with turbulence in mountain areas, when it is not windy, we dedicate this article to him.
How is the catabatic flow formed? at night the ground cools, and the air that touches the ground cools itself. As it cools, the air at the top of the mountain becomes denser (heavier) than the air that is at the same altitude and surrounds it, therefore, it tends to flow downhill towards the surrounding valleys. .
With adiabatic flow the opposite occurs and is less strong than catabatic. On the hillside where the air receives the sun, the air moves up and comes from the side of the mountain which gives it shade.
When you fly between mountains, you have to fly down the slope that the sun gives you, as long as you are not downwind. It must be remembered that turbulence created by the lee of a peak can cause structural failure of light aircraft. To minimize the risks of sinking currents or turbulence, fly over the tops of mountains as high as the performance of the aircraft and the oxygen system allows. In case of no wind, fly along the sunny Valley, as it produces updrafts and makes it easy to turn if necessary. The shaded area produces downdrafts.
When approaching a ridge, it is better to approach by following it rather than facing it, since if we encounter downdrafts, it is easier to escape by turning only 120º than 180º
It is important to know that the altimeters in mountain flights give errors, if the wind becomes stronger, as the air crosses the top the air pressure also reduces (Bernuille's principle).