Cloud

Question 1

How does cloud form?

Answer 1

Water vapour in the atmosphere condenses into small droplets of liquid water or ice crystals which are suspended in the atmosphere

Question 2

What are the four general cloud forms?

Answer 2

• Cirrus (threadlike, hairy, fine)
• Cumulus (Heaped or towering)
• Stratus (Sheet or Layer)
• Nimbus (Rain)

Question 3

How many genera are there?

Genera is the classification of cloud types

Answer 3

10

Question 4

How many etages are there?

Etage describes classification of clouds by height

Answer 4

3

Question 5

What are etages based off?

Answer 5

Altitude at which the base forms

Question 6

What altitude does a low etage form?

Answer 6

8500ft

Question 7

What altitude does middle etages form?

Answer 7

Between 8500ft and 20000ft

Question 8

What altitude do high etages form?

Answer 8

Above 20,000ft

Question 9

High Etage clouds?

Types…

Answer 9

• CI: Cirrus ( Fine strands, hooks or clumps of cloud)
• CS: Cirrostratus (A sheet of fine, hairy, wispy or thread like cloud)
• CC: Cirrocumulus (Cirrus forming in elements or lumps)

Question 10

What are high etage clouds composed of?

Answer 10

• Ice crystals and no precipitation falls from these clouds

Question 11

What is precipitation?

Answer 11

Rain or hail that reaches the ground

Question 12

What is Virga?

Answer 12

Rain or hail that doesn’t reach the ground

Question 13

Middle etage clouds?

Answer 13

• AS: Altostratus ( A sheet of middle level cloud, may produce rain or virga)
• AC: Altocumulus ( Heaped or lumpy cloud in middle layer, not usually associated with rain

Question 14

Low etage clouds?

Answer 14

• CU: Cumulus (Heaped or towering, may produce showers of rain or snow)
• CB: Cumulonimbus (Towering thunderstorm cloud producing heavy showers of rain, hail or snow)
• ST: Stratus (Low sheet of cloud, may produce drizzle)
• SC: Stratocumulus (Sheet of heaped or towering cloud, may produce drizzle)
• NS: Nimbostratus (Sheet of heavy rain, continuous rain or snow

Question 15

What are the two special form clouds?

Answer 15

• Castellatus

- Lenticularis

Question 16

Facts about Castellatus clouds…

Answer 16

• Generally associated with altocumulus
• Appears as a number of turret or cumuliform clouds by a common base
• Indicates instability and may signal later thunderstorm development

Question 17

Facts about Lenticularis cloud….

Answer 17

• Lens or almond shaped clouds indicating standing wave activity or mountain waves

Question 18

The type of cloud formed depends on….

Answer 18

• Stability or instability of atmosphere

- Some mechanism which lifts air causing it to cool adiabatically (Due to change in pressure)

Question 19

How does convection cause clouds?

Answer 19

Warm air rises as a result of surface heating. If conditions are unstable cumuliform cloud will form, perhaps resulting in cumulonimbus cloud if vertical development continues

Question 20

How does turbulence impact clouds?

Answer 20

Air may be lifted due to surface friction as wind blows over an uneven surface. If condensation occurs an undulating cloud base may form as water condenses in the up currents and evaporates in the down currents

Question 21

Orographic uplift

Answer 21

As air is forced up over a mountain range it cools adiabatically. The type of cloud formed will depend on the atmospheric stability. if stable conditions exist, stratiform cloud, often nimbostratus (with associated heavy rain) may form. if conditions are unstable, cumuliform clouds will develop

Question 22

What are mountain waves?

Answer 22

Standing waves generated as orographic uplift forces air up over a mountain range under the following conditions:

• Wind blowing at right angles to the range (Speed increasing with height to at least 25kts at the top of the range)
• Stable layer (An inversion) above the range

Question 23

If moisture is present lenticular clouds may form on the stationary crests of….

Answer 23

Standing waves

Question 24

A ragged rotor cloud may be present under the lenticular cloud, in the…

Answer 24

Turbulent rotor zone

Question 25

What is a front?

Answer 25

When two air masses of different temperatures meet, the warm air will be lifted; the boundary between the two air masses of varying temperature is called a front.

Question 26

What are fronts usually associated with?

Answer 26

Low pressure systems

Question 27

What is a cold front?

Answer 27

Cold air moves to undercut warm air and forces it to rise.

Question 28

A fast moving cold front tends to generate what type of conditions?

Answer 28

Unstable in the air ahead of it; this may result in frontal thunderstorms ahead of the front

Question 29

How is a cold front depicted on a synoptic chart?

Answer 29

A line with triangles pointing in the direction of movement

Question 30

A passage of a cold front in the southern hemisphere is marked by:

Answer 30

- Fall in temperature - Backing of the wind - A rise in pressure

Question 31

When warm air replaces cold air, the boundary is known as....

Answer 31

A warm front

Question 32

What happens in a warm front?

Answer 32

Warm air rides up over the cold air forming a boundary sloping in the direction of movement. The warm air is generally stable resulting in stratiform clouds, with rain from nimbostratus

Question 33

How is a warm front depicted on a synoptic chart?

Answer 33

Solid line with semi circles pointing in the direction of movement.

Question 34

What would indicate the approach of a warm front?

Answer 34

High level cloud, followed by mid level cloud and eventually extensive nimbostratus

Question 35

The passage of warm front is marked by...

Answer 35

- Rise in temperature - Backing of wind - The pressure fall decreasing

Question 36

What is an occluded front?

Answer 36

A cold front which has caught up to a warm front

Question 37

How is an occluded front represented on synoptic chart?

Answer 37

Circles and triangles pointing in same direction on line.

Question 38

What is the weather associated with an occluded front?

Answer 38

Both warm and cold front type weather, often with extensive cloud and widespread rain

Question 39

What is an Quasi-stationary front?

Answer 39

Warm and Cold front meet from different directions

Question 40

How is a Quasi-stationary front represented on synoptic chart?

Answer 40

Triangles and circles pointing in opposite directions of line