Clouds and Fog Quiz

Questions and Answers

What does a mid-latitude cumulonimbus cloud typically contain?

Only water droplets

Ice crystals, water droplets and super cooled water droplets (correct)

Only ice crystals

Ice crystals and water droplets but never super cooled water droplets

Which cloud type is classified as high level?

C1 (correct)

Which of the following clouds are classified as medium level clouds?

Cumulonimbus

Cirrocumulus and cirrostratus

All convective clouds

Altostratus and altocumulus (correct)

When flying in cirrus clouds, which flying condition may be encountered?

Average visibility more than 1000m; nil icing Signup and view all the answers

What is the expected height above ground for the base of a uniform SC cloud layer in Western Europe with an average height of 500m?

1500 – 7000 ft above ground Signup and view all the answers

Clouds that extend over low, medium, and high levels are classified as which type?

CB Signup and view all the answers

Which clouds are evidence of stable air conditions?

ST, AS Signup and view all the answers

What atmospheric condition is indicated by strongly developed cumulus clouds?

Instability in the atmosphere Signup and view all the answers

What are fall-streaks or virga?

Water or ice particles falling out of a cloud that evaporate before reaching the ground Signup and view all the answers

What layer defines low-level clouds bases?

The surface to 6500 ft Signup and view all the answers

Which of the following is a cause of stratus forming over flat land?

Radiation during the night from the earth surface in moderate wind Signup and view all the answers

What process in an air mass leads to the creation of wide spread NS, AS and ST cloud coverage?

Lifting Signup and view all the answers

Which type of cloud is described as a generally grey cloud layer with a uniform base that can produce drizzle or snow grains?

Stratus Signup and view all the answers

Which of the following clouds are classified as medium level clouds in temperate regions?

AS, AC Signup and view all the answers

Which types of clouds are evidence of unstable air conditions?

CU, CB Signup and view all the answers

Which displayed cloud form is representative of altocumulus castellanus?

C Signup and view all the answers

Which of the following processes within a layer of air may lead to the building of CU and CB clouds?

Convection Signup and view all the answers

Which of the following cloud types is classified as a medium level cloud?

AS Signup and view all the answers

At what altitude range can high level clouds typically be found?

15000 – 35000 ft above the terrain Signup and view all the answers

What is the main composition of high level clouds?

Ice crystals Signup and view all the answers

What are the characteristics of cumuliform clouds?

Large water droplets, instability, turbulence, showers and mainly clear ice Signup and view all the answers

If a uniform altocumulus cloud layer is present over a plain in Western Europe at 500m, how high above ground is the base of this cloud likely to be?

7000 – 15000 ft above the terrain Signup and view all the answers

What does the presence of altocumulus lenticularis indicate?

Presence of mountain waves Signup and view all the answers

In which scenario is moderate to severe airframe icing most likely to occur?

In Nimbostratus cloud Signup and view all the answers

Cumulus clouds are an indication of what atmospheric condition?

Up and downdrafts Signup and view all the answers

What does the presence of altocumulus castellanus signify?

Instability in the middle troposphere Signup and view all the answers

Which cloud type is typically associated with steady rain or snowfall?

Nimbostratus Signup and view all the answers

How can one distinguish between altostratus and nimbostratus clouds?

The cloud base is higher in AS and precipitation, if any, is light Signup and view all the answers

What effect does a thin coating of hoar frost have on wing lift?

It has deleterious effects on the lift of the wing Signup and view all the answers

Which type of precipitation is associated with the most severe icing conditions?

Freezing rain Signup and view all the answers

What type of icing will most likely be encountered after descending into humid air from very cold conditions?

Hoar frost Signup and view all the answers

At what altitude range is the probability of airframe icing highest when descending through clouds with a freezing level at FL 60?

Between FL 120 and FL 60 Signup and view all the answers

When flying into supercooled rain at temperatures below 0°C, what type of icing is most likely?

Clear ice Signup and view all the answers

What is the primary mechanism through which icing occurs in layered clouds?

Freezing of supercooled liquid droplets Signup and view all the answers

What type of ice is characterized by a white and rough powder-like contamination along the leading edge of the wing?

Rime ice Signup and view all the answers

Under which condition is an aircraft most susceptible to icing?

Level flight below a rain-producing cloud when OAT is below zero degrees C Signup and view all the answers

Which statement correctly describes a risk factor for aircraft icing?

A cloud consisting of both supercooled cloud droplets and ice crystals produces aircraft icing Signup and view all the answers

When is hoar frost most likely to form?

Taking off from an airfield with a significant ground inversion Signup and view all the answers

Which factor most significantly affects the formation of different ice types on an aircraft?

Cloud temperature and droplet size Signup and view all the answers

In which situation do fog droplets exist in a state that defines freezing fog?

Are supercooled Signup and view all the answers

Which scenario presents a higher risk for icing based on cloud types?

Descending through deep nimbostratus clouds Signup and view all the answers

For two aircraft flying through the same cloud, which wing profile is more likely to experience a greater accumulation of ice?

The aircraft with a thick wing profile Signup and view all the answers

What condition contributes to the formation of clear ice?

Large droplets at just below freezing Signup and view all the answers

Under which circumstances can moderate icing be safely tolerated according to ICAO recommendations?

Light icing Signup and view all the answers

What is the primary cause of hoar frost formation on an aircraft?

Water vapor directly freezing Signup and view all the answers

Which statement is accurate regarding moderate-to-severe airframe icing?

It may happen in a cumulonimbus capillatus. Signup and view all the answers

Which condition indicates the potential for severe icing based on a vertical temperature profile?

Intersecting the 0°C isotherm twice Signup and view all the answers

Why is icing over hills often more severe than over flat terrain?

Orographic lifting raises the freezing level. Signup and view all the answers

Under which condition does rime ice formation occur during flight?

Droplets freeze rapidly and do not spread out. Signup and view all the answers

Which mechanism correctly describes the formation of clear ice in freezing rain?

Formed by the freezing of large water drops. Signup and view all the answers

What effect does icing on wings typically have during flight operations?

Increases the stalling speed of the aircraft. Signup and view all the answers

What does icing on an aircraft typically cause?

Stalling speed to increase. Signup and view all the answers

Which aircraft is likely to experience more icing?

Aircraft S experiences more icing than T Signup and view all the answers

What can be expected on a winter day in northern Europe with a thick layer of stratocumulus clouds at close to zero degrees C?

A high probability for icing in clouds, severe icing in the upper part due to large droplets Signup and view all the answers

Which cloud types are most likely to produce light to moderate icing when not subject to orographic lifting?

Altocumulus and altostratus Signup and view all the answers

At what degree of icing should ICAOs change course and/or altitude immediately?

Severe Signup and view all the answers

Clear ice forms on an aircraft by the freezing of which type of water?

Large super cooled water drops Signup and view all the answers

What is a significant danger of clear ice on aircraft?

It is heavy and difficult to remove from the aircraft surfaces Signup and view all the answers

In which environment is there likely the highest rate of aircraft structural ice accumulation?

Freezing rain Signup and view all the answers

Under what conditions should ICAOs be recommended to change course and/or altitude?

Moderate Signup and view all the answers

At which flight level is the risk for aircraft icing in cloud the greatest?

FL 150 Signup and view all the answers

What process leads to the formation of clear ice on an aircraft?

Super cooled water droplets spreading during the freezing process Signup and view all the answers

Study Notes

Cloud Formation and Description

Stratus clouds often form over flat land at night due to radiation cooling from the Earth's surface combined with moderate wind.
Widespread cloud coverage of Nimbostratus (NS), Altostratus (AS), and Stratus (ST) typically results from lifting processes in an air mass.
Cumulus clouds indicate unstable air conditions, including cumulus (CU) and cumulonimbus (CB) types.
Medium level clouds in temperate regions include Altostratus (AS) and Altocumulus (AC).
Cumulonimbus clouds contain ice crystals, water droplets, and supercooled water droplets, especially in mid-latitudes during summer.

Cloud Types and Levels

Low-level clouds extend from the surface up to 6500 ft, with Stratus (ST) classified as a low-level cloud.
Medium-level cloud types include Altostratus (AS) and Altocumulus (AC).
High-level clouds, such as Cirrus (CI), are primarily made up of ice crystals.
Nimbostratus clouds can extend through multiple layers, offering steady precipitation.

Cloud Characteristics

Altostratus clouds belong to medium-level clouds and can be distinguished by their higher cloud base and lighter precipitation compared to Nimbostratus.
Cumuliform clouds indicate turbulence and instability, characterized by significant vertical development.
Fall-streaks (virga) are water or ice particles that evaporate before reaching the ground.

Conditions Impacting Clouds

Strongly developed cumulus can indicate atmospheric instability and the presence of vertical air movements.
Altocumulus lenticularis suggests the presence of mountain waves, often associated with orographic effects.
Moderate to severe airframe icing is likely encountered in Nimbostratus clouds.

Identifying Clouds

Stratus clouds may produce drizzle or snow grains; Nimbostratus clouds produce continuous rain or snow.
Altostratus can have a higher base than Nimbostratus, and precipitation from Altostratus, if present, is typically light.
Cumulonimbus clouds can extend into the stratosphere, showing significant vertical development.

Summary of Key Facts

Altostratus and Nimbostratus clouds can be confused; however, Altostratus typically has a higher cloud base and lighter precipitation.
Cumulus clouds are indicative of up and downdrafts and generally signify unstable conditions.
Understanding cloud types and their formation is essential for aviation safety and weather forecasting.

Aircraft Icing Types and Risks

Contamination along wing surfaces can include rime ice, which occurs when small supercooled droplets freeze on impact.
Aircraft are most susceptible to icing during level flight below rain-producing clouds with temperatures below zero degrees Celsius.
The highest risk of icing arises from clouds containing both supercooled droplets and ice crystals.

Formation Conditions

Hoar frost is likely to form from a ground inversion, particularly during takeoff.
Key factors in the formation of various types of aircraft icing include cloud temperature and droplet size.
Freezing fog is defined as existing when fog droplets are supercooled.

Ice Accretion Dynamics

Aircraft with sharp wing profiles experience less icing compared to those with thick profiles when flying through supercooled droplet clouds.
Significant icing is likely in stratus clouds during winter, particularly in northern Europe with temperatures near zero.
Light to moderate icing typically occurs in altostratus and altocumulus clouds with supercooled droplets.

Severity and Guidelines

ICAO recommendations indicate immediate course and altitude changes at the severe ice level.
Clear ice forms predominantly from the freezing of large supercooled water drops, making it particularly dangerous due to its weight and removal difficulty.
The heaviest clear ice accretion often occurs in cumulonimbus clouds at temperatures between -2°C and -15°C.

Environmental and Flight Considerations

The rate of structural ice accumulation is highest in environments with freezing rain, leading to severe icing conditions.
Pilots facing heavy freezing rain should turn back before experiencing a loss of maneuverability.
During descent through humid air masses from very cold conditions, hoar frost is expected due to water vapor freezing onto cold surfaces.

Impact on Flight Performance

Ice accumulation significantly increases the stalling speed of an aircraft, which can lead to dangerous flight conditions.
A thin layer of hoar frost negatively affects wing lift, emphasizing the importance of ice removal prior to flight.
Freezing rain poses the most severe icing threat, as large water drops freeze upon impact with aircraft surfaces.

Associated Risks

Understanding the temperature profile in the atmosphere is crucial in predicting icing conditions, especially when the 0°C isotherm intersects multiple times.
Orographic lifting enhances the severity of icing due to increased moisture retention in clouds above hilly terrains.
Pilots must be aware of icing formations associated with various weather conditions and react appropriately to maintain safe flight operations.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on cloud formation and types in this quiz focused on Clouds and Fog. Questions cover various processes that lead to the formation of different cloud types and conditions. Ideal for aviation students and weather enthusiasts.