Page 291 - PPL-engelsk 2025

Meteorology

3.6.7 Fog, mist, haze, dew and rime

3.6.7.1 Fog and mist

Mist can form when humidity is high, and the temperature is close to the dew

point. The mist is usually not very dense, and visibility can be reduced in a

limited area.

Mist resembles fog, but it is less dense and causes less visibility reduction than

fog. Visibility is often between 1 and 5 km.

Mist consists of small water droplets, but unlike fog, these droplets are much
finer and are distributed in the air in a much thinner layer, meaning visibility is

better than in fog, but it may be slightly blurred.

When it is misty, it is indicated as BR – from the French word “Brume,” which

means mist.

3.6.7.2 Haze

Dry mist, Haze, is a type of mist where it is not humidity that reduces visibility,

but pollution particles in the air.

When flying in mist, visibility is very poor when flying towards the sun. Flying

with the sun behind you, however, provides much better visibility.

It usually comes with the advection of continental tropical air from a

southeastern direction.

Dry mist is indicated as HZ, and the English term is Haze.

3.6.7.3 Dew and rime

If there is no wind, the ground can cool down significantly without the air above

it cooling to the same extent.

The surface of the ground and objects on it can therefore reach the air's dew

point temperature. As a result, some of the air's water vapor condenses directly

onto the ground and objects as water droplets.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 291