Page 223 - PPL-engelsk 2025

Meteorology

3.3.3 Temperature dependence on altitude and air mass

In the atmosphere, temperature varies with altitude depending on the season,

location and time of day.

Here is an illustration of how a radiosonde is

used to measure temperature at different

altitudes.

The numbers on the far right of the illustration (-
10 to 20) indicate the normal temperature at a

certain altitude, corresponding to the numbers

on the left of the illustration.

Here, calculations have been made on the

temperature and humidity conditions for two

different air masses: an almost dry air mass and

a humid air mass.

Air that is warmer than the surrounding air will tend to rise.

If we take the air masses, the dry one on the left and the humid one on the
right, as a starting point, their temperature at ground level is the same as the

surroundings, and they will remain where they are.

The humid air will become warmer than the surrounding air as it rises. This

happens as a result of cloud formation, which releases heat. The released heat

causes the air to rise further and form clouds with a vertical structure.

The dry air on the left will not tend to rise.

However, if there is wind and sloping terrain, it can happen that the air masses
rise higher in the atmosphere and the surrounding air pressure will decrease.

This will cause the rising air mass to expand, and there will be a drop in

temperature in the air. At the same time, the humidity will increase.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 223