Clouds

Question 1

High cloud are referred to as -

Bases above a height of -

Answer 1

Cirro clouds

20 000ft

Question 2

Medium cloud are referred as -

bases between heights of -

Answer 2

Alto

8 000ft and 20 000ft

Question 3

Low cloud are referred as -

Bases below -

Answer 3

Strato

8 000ft

Question 4

State the classification of cloud types:

High -

Medium -

Low -

Vertical Development cloud -

Clouds may be further subdivided into individual types according to their appearance:

Answer 4

High cloud have bases above 20 000ft and go by the name CIRRO

Medium clouds have bases between 8 000ft and 20 000ft and are known as ALTO clouds

Low clouds have bases below 8 000ft and known as LAYER or STRATOFORM cloud

Vertical clouds that develop through one or more of the above and are known as CUMULOFORM

Question 5

Water vapour only become visible after condensation. Condensation require the air mass to cool sufficiently to dew point. The four possible ways cloud can form:

The 5 ways cloud can form due to adiabatic cooling:`

Answer 5

1. Loss of heat by radiation from the air
2. Mixing of two air masses at different temperature with sufficient moisture content
3. Loss of heat by conduction with a cold surface
4. Adiabatic cooling by lifting(by far the most important factor in the vertical formation of cloud)
5. Orographically
6. Convergence
7. Convection
8. Frontal

Question 6

The cloud types that are formed due to orographic uplift:

Answer 6

Cloud of stratus or layer type and sometimes cumulus or nimbostratus. When, on occasions, the air is unstable, stratocumulus cloud will develop into cumulus or even cumulonimbus.

Question 7

The cloud types that are formed due to convergence:

Answer 7

Cloud formation due to convergent uplift is normally of the cumulus type, developing into cumulonimbus when the air is unstable.

Question 8

Explain the “Adiabatic process”:

Answer 8

Air that is forced to rise enters an area of successively lower pressure. The air will consequently expand and cooling will occur due to the heat distributed over a larger volume. Conversely, air that is forced to descent will heat up due to compression.

Question 9

Explain the formation of cloud due to convection:

Answer 9

During the day, certain more conductive surfaces heat up faster than others such as ploughed fields. The heated surface will expand and, being less dense, rise. These currents are referred to as “thermals”. Say the ELR is 1c / 1000ft and the surface temperature is +10, but the thermal air surface is +12, the air will continually rise(since the DALR is 3c / 1000ft) up till dew point where the lapse rate will slow to 1.5c/1 000ft. There will be a point where the risen air will equal the surrounding atmospheric air. This will cause cumulus cloud to form, but since the atmosphere is stable, the cloud tops will not exceed 5 000ft.

Flying conditions below the cloud will be turbulent while above will be smooth.

If instability persists(ELR > DALR/SALR) cumulonimbus cloud will form with great vertical extend

Question 10

What is the cloud “base” -

When is the word “Ceiling” used?

Answer 10

Cloud base is the height of the base of the cloud above official aerodrome level.

When more than half the sky is covered by cloud below 20 000ft

Question 11

The hazards of clouds:

Answer 11

1. Turbulence
2. Poor visibility
3. Icing
4. Rain
5. Lightning