Category Archives: Meteorology


In a layer of air the decrease in temperature per 100 metres increase in height is more than 1(degrees)C. This layer can be described as being

A: conditionally unstable
B: absolutely stable
C: absolutely unstable
D: conditionally stable









Answer: C


The stability/instability of air can be determined by comparing the DALR or SALR to the ELR.

DALR = 3 degrees/1000ft
0.95 degrees/100m
SALR = 1.8 degrees/1000ft
0.6 degrees/100m

If the ELR < 1.8 degrees/1000ft…air is stable,
because a rising parcel of air will cool to the dry or saturated Lapse rate. These are both more than the ELR. So the parcel of air is cooling faster than the environment and as soon as the parcel has no more rising force it will sink back because it is colder and heavier than the surrounding air.

If the ELR > 3 degrees/1000ft…the air is unstable,
the rising parcel of air will be warmer than the air around it. So it keeps rising.

If the ELR is inbetween 1.8 and 3:
1.8 degrees/1000ft < ELR < 3 degrees/1000ft
the the air is conditionally unstable.
It is conditional because the rising force needs to be strong enough to bring the air packet to an altitude where it will become unstable.

In this question the ELR is MORE THAN 1 degree/100m which means it is over 3 degrees/1000ft so the parcel is absolutely unstable.

In the northern hemisphere the wind at the surface blows

A: clockwise around, and away from the centre of, a low pressure area
B: from a low pressure area to a high pressure area
C: counter-clockwise around, and toward the centre of, a low pressure area
D: counter-clockwise around, and away from the centre of, a high pressure area.









Answer: C

After a clear night cumuliform clouds are formed in the morning. Why can the base of these clouds become higher during the day?

A: Because the stability increases.
B: The wind speed is increasing, because the cold air mass changes into a warm air mass.
C: Because the surface temperature increases.
D: Because the difference between the temperature and the dewpoint temperature at the initial condensation level becomes smaller.









Answer: C

The turbulence which occurs at high flight levels (above FL 250) is mainly of the type Clear Air Turbulence. In what way can moderate to severe Clear Air Turbulence affect an aircraft, the flight and the passengers?

A: The turbulence can be resembled with the roughness of a washing-board (small scale) and will not have influence on the aircraft and its solidity, but will make flight a little more difficult. The passengers will seldom notice anything of this turbulence.
B: The turbulence is a large scale one (waving) so that the aircraft will be difficult to manoeuvre. The passengers will feel some discomfort.
C: The turbulence is a small scale one and can cause damage. The manoeuvring of the aircraft will be made more difficult or even impossible. For the passengers the flight will be unpleasant.
D: The turbulence is wave like which makes the flight unpleasant for the passengers but the manoeuvring will not be affected essentially.









Answer: C