Page 273 - PPL-engelsk 2025

Meteorology

3.5.5 Adiabatic processes

Adiabatic processes are processes where no heat (energy) is exchanged with

the surroundings.

There are two types of adiabatic processes:

- Dry adiabatic process
- Saturated adiabatic process

3.5.5.1 Dry adiabatic process

A dry adiabatic process occurs in dry, unsaturated air.

This process determines the temperature rise or fall in descending or ascending

dry and unsaturated air when there is no heat exchange with the surroundings.

The dry adiabatic lapse rate is 3°C per 1,000 feet (1°C per 100 meters). This
means that when dry air is lifted 1,000 feet, the expansion results in a

temperature drop of 3°C.

3.5.5.2 Saturated adiabatic process

A moist adiabatic process determines the temperature fall or rise in ascending

or descending saturated air, where there is no heat exchange with the

surroundings.

When saturated air rises, latent heat is released during the condensation of
water vapor, which reduces the temperature drop compared to dry

unsaturated air.

The saturated adiabatic lapse rate is 1.5°C per 1,000 feet (½°C per 100 meters).

This means that when dry air is lifted 1,000 feet, the expansion results in a

temperature drop of 1.5°C.

o
o
The dry adiabat is 3 C per 1000 feet (1 C per 100 meters)
o
o
The saturated adiabat is 1.5 C per 1000 feet (½ C per 100 meters)

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 273