Page 281 - PPL-engelsk 2025

Meteorology

3.6.3 Formation of clouds

All clouds are formed when a volume of air containing water vapor is cooled to

a temperature below the air's dew point.

At this point, part of the water vapor "forces" itself to condense into liquid

water, and it is this water that forms the countless tiny droplets that make up
the cloud.

Clouds primarily form in three different ways depending on the meteorological

conditions:

- Through convection

- Through fronts / advection

- Through orography

3.6.3.1 Convective clouds

Convective clouds are of the cumulus type, meaning they have vertical

development. Convective clouds form through adiabatic cooling, which is when

rising clear air cools down and forms clouds. When the sun's heat warms the

earth's surface, the air close to the ground warms up, and this warm air rises

into the atmosphere. As the air rises, it cools, and the water vapor condenses,

creating clouds. This process is called convection.

An example would be fair-weather cumulus clouds, which form on clear

summer days when the air isn't too humid.

The height of the cloud base can be reasonably calculated by taking the

difference between the temperature and dew point temperature and
multiplying by 400 feet.

3.6.3.2 Front clouds / advection clouds

These clouds form when air is carried over a cool surface or cooler air. Clouds

formed in this way are elongated clouds with little vertical extent, and there is

stability beneath the clouds.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 281