atsc 113 final exam Questions with
Correct Answers
FLYING SECTION:
normal clouds - ANSWERS- classified into two categories
1. convective clouds/ cumuliform clouds (Cu)
- look like stacks of cotton balls -- are associated with updrafts
2. layer clouds/ stratiform clouds (St)
- look like sheets or blankets that can extend hundreds of kilometers horizontally.
cumuliform clouds - ANSWERS
cumuliform continued - ANSWERS- form when warm humid air rises through cooler
surrounding air in the atmosphere
- the buoyancy associated w/ the warm air drives strong updrafts
- even more buoyancy is created as water vapour in the air condenses to become cloud
droplets bc condensation releases latent heat (energy required during a phase change
— condensation)
- often have flat bases that are somewhat near to the ground (~ 1km above ground)
- four types of clouds
1. small = cumulus humilis (aka fair weather cumulus)
2. medium = cumulus mediocris
3. large = cumulus congestus (aka towering cumulus)
4. extra large = cumulonimbus (aka thunderstorms)
how do cumuliform clouds form? - ANSWERS- wherever the air near the ground is
colder than the ground or ocean-surface.
this can happen:
- behind cold fronts (where a warm air mass is forced upwards by collision with a cold
air mass)
- on mostly clear days when sunshine warms the ground more than the overlying air
- over urban and industrial centres that are warmer than the surrounding rural areas
- when cold air blows over a warmer ocean or lake, or over warmer land
** also mountains can trigger all sizes of cumulus clouds, including thunderstorms
,cumuliform local effects - ANSWERS- usually an updraft starts near ground level and
extends up into the cloud all the way to the cloud top
- birds and sailplane pilots intentionally circle in the updrafts to get a free lift to higher
altitude
- between the updrafts are weaker downdrafts of clear air
- airplane and helicopter pilots flying at a constant altitude below cloud base would feel
a bumpy ride as they fly through the up- and down-drafts
- at earth's surface, downdrafts of air hitting the ground causes windgusts that sailors
can see as slightly rougher, darker-looking patches of water called "cat's paws"
- similar gusts over pastures and grain crops can cause wavy fields of grain.
cumuliform hazards - ANSWERS- deeper cumuliform clouds have stronger updrafts
- deepest ones (cumulus congestus and thunderstorms) have such violent updrafts that
they can be a hazard to aircraft
- the strong updrafts can cause the pilot to lose control of the aircraft/ can over-stress
the aircraft causing things to break
- the medium and smaller cumulus can be flown under and through but will cause a
bumpy ride
stratiform cloud - ANSWERS
stratocumulus clouds - ANSWERS- low-altitude layer of lumpy clouds
- don't fit well in the normal cumuliform or stratiform groups, but have characteristics of
both groups
- look like sheets or blankets
- range from only 100 m - 6 km thick in the vertical but can have a horizontal extent of
100 km to 1000 km
- are associated with layers in the atmosphere with different relative temperatures
- imagine a wedge of cool or cold air at ground level
- when a horizontal wind moves warmer air toward this cold wedge, the warm air slides
up along the top surface of the cold air bc the warm air is more buoyant (lighter) than
the cold air
- this behavior is typical of warm fronts
- as warm air rises, it gradually cools to the point where water vapour can condense and
make clouds
- often find stratiform clouds along warm fronts
,types of stratiform clouds - ANSWERS- are classified by their altitude into 3 categories:
1. high = cirrus cirrostratus and cirrocumulus
2. medium = altostratus and altocumulus
3. low: stratus and nimbostratus
order of stratiform movement - ANSWERS- as a warm front approaches, you see the
high clouds first
- these clouds extend hundreds of km ahead of the front, so you see them about half a
day before the warm front arrives
- next comes the mid-level clouds, and finally the low clouds along with drizzle or light
rain/snow
stratiform hazards - ANSWERS- not usually turbulent so flying through them is often a
smooth ride
- but inside any cloud, including stratiform clouds, pilots need to be flying on instruments
bc they cannot see the ground or landmarks
- if the stratiform clouds are cold enough (at temperatures just below freezing) ice forms
on the leading edges of the aircraft due to the quick freezing of supercooled (below
freezing) liquid water drops
- soarplane pilots usually don't like stratiform clouds because they shade the ground
and prevent thermal updrafts from forming
special clouds
- associated with unstable air aloft - ANSWERSClouds in unstable air aloft
1. castellanus
- look like small castle turrets
- a clue that the atmosphere is becoming unstable; thunderstorms possible later in the
day
- bumpy if you are flying in that cloud layer, but smooth air above and below it.
2. billow (K-H wave) clouds
- indicate wind shear (change of wind speed or direction) and clear-air turbulence (CAT)
(moderate to strong bumps) at aircraft altitudes
- smoother air is often above and below the layer of billow clouds
castellanus clouds (special clouds) - ANSWERS- most convective clouds (ex: cumulus
clouds) are caused by warm air rising from the earth's surface
- for these clouds the cloud diameter is roughly equal to the height of the cloud top
above ground
-but sometimes a thin layer of cold air will form above a thin layer of warm air
- this combination of layers are said to be statically unstable
, - as the warm air rises and the cold air sinks within this warm-cold-air sandwich,
mineature convective clouds form in the rising air if enough water vapour is present
- these clouds look like castle turrets, which is how they get their name castellanus
- these castle turrets sometimes form out of the top of a layer of clouds so they are a
type of stratiform cloud
- for these clouds their diameter is small compared to their altitude above ground
- convective circulations of these clouds do not touch the ground and instead are
contained within that warm-cold-air sandwich layer
castellanus clouds forms - ANSWERS1. high-altitude clouds (cirrus castellanus or
cirrocumulus castellanus)
2. mid-altitude clouds (altocumulus castellanus)
3. low-altitude clouds (stratocumulus castellanus)
castellanus clouds: tips for pilots - ANSWERS- instrument-rated pilots should avoid
flying in a layer of castellanus clouds bc likely be turbulent
- if you accidentally find yourself in a layer of castellanus cloud, usually climbing or
descending a small distance will get you out of the layer of turbulence
- pilots can use these clouds as a clue that the atmosphere contains some instability,
which can allow thunderstorms to form more easily later in the day
- storm chasers like castellanus clouds bc of this
- but a layer of castellanus clouds does not guarantee that thunderstorms will form later
billow clouds (special clouds) - ANSWERS- wind shear (change of wind speed or
direction with height) in the atmosphere can cause waves to form in a layer of air where
cooler air underlies warmer air
- these waves called Kelvin-Helmholtz (KH) waves and do not need mountains to form
- these waves have short wavelengths and are relatively thin (hundreds of meters)
- such waves probably occur very often in the atmosphere but are visible only rarely,
when the rising cool air is relatively humid
- under the correct conditions, parallel bands of clouds form in the crest of each wave
- from the ground, these parallel bands of clouds look like billows of an accordion
- waves often break causing that cloud layer to become turbulent
- while waves are breaking, "cat's eye" swirls form, some of which are even visible on
radar
- pilots prefer to avoid flying at these altitudes because of the turbulence induced by
wind shear
Correct Answers
FLYING SECTION:
normal clouds - ANSWERS- classified into two categories
1. convective clouds/ cumuliform clouds (Cu)
- look like stacks of cotton balls -- are associated with updrafts
2. layer clouds/ stratiform clouds (St)
- look like sheets or blankets that can extend hundreds of kilometers horizontally.
cumuliform clouds - ANSWERS
cumuliform continued - ANSWERS- form when warm humid air rises through cooler
surrounding air in the atmosphere
- the buoyancy associated w/ the warm air drives strong updrafts
- even more buoyancy is created as water vapour in the air condenses to become cloud
droplets bc condensation releases latent heat (energy required during a phase change
— condensation)
- often have flat bases that are somewhat near to the ground (~ 1km above ground)
- four types of clouds
1. small = cumulus humilis (aka fair weather cumulus)
2. medium = cumulus mediocris
3. large = cumulus congestus (aka towering cumulus)
4. extra large = cumulonimbus (aka thunderstorms)
how do cumuliform clouds form? - ANSWERS- wherever the air near the ground is
colder than the ground or ocean-surface.
this can happen:
- behind cold fronts (where a warm air mass is forced upwards by collision with a cold
air mass)
- on mostly clear days when sunshine warms the ground more than the overlying air
- over urban and industrial centres that are warmer than the surrounding rural areas
- when cold air blows over a warmer ocean or lake, or over warmer land
** also mountains can trigger all sizes of cumulus clouds, including thunderstorms
,cumuliform local effects - ANSWERS- usually an updraft starts near ground level and
extends up into the cloud all the way to the cloud top
- birds and sailplane pilots intentionally circle in the updrafts to get a free lift to higher
altitude
- between the updrafts are weaker downdrafts of clear air
- airplane and helicopter pilots flying at a constant altitude below cloud base would feel
a bumpy ride as they fly through the up- and down-drafts
- at earth's surface, downdrafts of air hitting the ground causes windgusts that sailors
can see as slightly rougher, darker-looking patches of water called "cat's paws"
- similar gusts over pastures and grain crops can cause wavy fields of grain.
cumuliform hazards - ANSWERS- deeper cumuliform clouds have stronger updrafts
- deepest ones (cumulus congestus and thunderstorms) have such violent updrafts that
they can be a hazard to aircraft
- the strong updrafts can cause the pilot to lose control of the aircraft/ can over-stress
the aircraft causing things to break
- the medium and smaller cumulus can be flown under and through but will cause a
bumpy ride
stratiform cloud - ANSWERS
stratocumulus clouds - ANSWERS- low-altitude layer of lumpy clouds
- don't fit well in the normal cumuliform or stratiform groups, but have characteristics of
both groups
- look like sheets or blankets
- range from only 100 m - 6 km thick in the vertical but can have a horizontal extent of
100 km to 1000 km
- are associated with layers in the atmosphere with different relative temperatures
- imagine a wedge of cool or cold air at ground level
- when a horizontal wind moves warmer air toward this cold wedge, the warm air slides
up along the top surface of the cold air bc the warm air is more buoyant (lighter) than
the cold air
- this behavior is typical of warm fronts
- as warm air rises, it gradually cools to the point where water vapour can condense and
make clouds
- often find stratiform clouds along warm fronts
,types of stratiform clouds - ANSWERS- are classified by their altitude into 3 categories:
1. high = cirrus cirrostratus and cirrocumulus
2. medium = altostratus and altocumulus
3. low: stratus and nimbostratus
order of stratiform movement - ANSWERS- as a warm front approaches, you see the
high clouds first
- these clouds extend hundreds of km ahead of the front, so you see them about half a
day before the warm front arrives
- next comes the mid-level clouds, and finally the low clouds along with drizzle or light
rain/snow
stratiform hazards - ANSWERS- not usually turbulent so flying through them is often a
smooth ride
- but inside any cloud, including stratiform clouds, pilots need to be flying on instruments
bc they cannot see the ground or landmarks
- if the stratiform clouds are cold enough (at temperatures just below freezing) ice forms
on the leading edges of the aircraft due to the quick freezing of supercooled (below
freezing) liquid water drops
- soarplane pilots usually don't like stratiform clouds because they shade the ground
and prevent thermal updrafts from forming
special clouds
- associated with unstable air aloft - ANSWERSClouds in unstable air aloft
1. castellanus
- look like small castle turrets
- a clue that the atmosphere is becoming unstable; thunderstorms possible later in the
day
- bumpy if you are flying in that cloud layer, but smooth air above and below it.
2. billow (K-H wave) clouds
- indicate wind shear (change of wind speed or direction) and clear-air turbulence (CAT)
(moderate to strong bumps) at aircraft altitudes
- smoother air is often above and below the layer of billow clouds
castellanus clouds (special clouds) - ANSWERS- most convective clouds (ex: cumulus
clouds) are caused by warm air rising from the earth's surface
- for these clouds the cloud diameter is roughly equal to the height of the cloud top
above ground
-but sometimes a thin layer of cold air will form above a thin layer of warm air
- this combination of layers are said to be statically unstable
, - as the warm air rises and the cold air sinks within this warm-cold-air sandwich,
mineature convective clouds form in the rising air if enough water vapour is present
- these clouds look like castle turrets, which is how they get their name castellanus
- these castle turrets sometimes form out of the top of a layer of clouds so they are a
type of stratiform cloud
- for these clouds their diameter is small compared to their altitude above ground
- convective circulations of these clouds do not touch the ground and instead are
contained within that warm-cold-air sandwich layer
castellanus clouds forms - ANSWERS1. high-altitude clouds (cirrus castellanus or
cirrocumulus castellanus)
2. mid-altitude clouds (altocumulus castellanus)
3. low-altitude clouds (stratocumulus castellanus)
castellanus clouds: tips for pilots - ANSWERS- instrument-rated pilots should avoid
flying in a layer of castellanus clouds bc likely be turbulent
- if you accidentally find yourself in a layer of castellanus cloud, usually climbing or
descending a small distance will get you out of the layer of turbulence
- pilots can use these clouds as a clue that the atmosphere contains some instability,
which can allow thunderstorms to form more easily later in the day
- storm chasers like castellanus clouds bc of this
- but a layer of castellanus clouds does not guarantee that thunderstorms will form later
billow clouds (special clouds) - ANSWERS- wind shear (change of wind speed or
direction with height) in the atmosphere can cause waves to form in a layer of air where
cooler air underlies warmer air
- these waves called Kelvin-Helmholtz (KH) waves and do not need mountains to form
- these waves have short wavelengths and are relatively thin (hundreds of meters)
- such waves probably occur very often in the atmosphere but are visible only rarely,
when the rising cool air is relatively humid
- under the correct conditions, parallel bands of clouds form in the crest of each wave
- from the ground, these parallel bands of clouds look like billows of an accordion
- waves often break causing that cloud layer to become turbulent
- while waves are breaking, "cat's eye" swirls form, some of which are even visible on
radar
- pilots prefer to avoid flying at these altitudes because of the turbulence induced by
wind shear
