Aviation Weather Flashcards

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Questions and Answers

In which environment is aircraft structural ice most likely to have the highest accumulation rate?

Freezing rain (correct)

Cumulus clouds with below freezing temperatures

Freezing drizzle

Why is frost considered hazardous to flight?

Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability (correct)

Frost changes the basic aerodynamic shape of the airfoils, thereby increasing lift

Frost slows the airflow over the airfoils, thereby increasing control effectiveness

How does frost affect the lifting surfaces of an airplane on takeoff?

Frost may prevent the airplane from becoming airborne at normal takeoff speed (correct)

Frost will change the camber of the wing, increasing lift during takeoff

Frost may cause the airplane to become airborne with a lower angle of attack at a lower indicated airspeed

The conditions necessary for the formation of cumulonimbus clouds are a lifting action and

Unstable, moist air Signup and view all the answers

What feature is normally associated with the cumulus stage of a thunderstorm?

Continuous updraft Signup and view all the answers

Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?

Precipitation beginning to fall Signup and view all the answers

What conditions are necessary for the formation of thunderstorms?

High humidity, lifting force, and unstable conditions Signup and view all the answers

During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts?

Dissipating Signup and view all the answers

Thunderstorms reach their greatest intensity during the

Mature stage Signup and view all the answers

Thunderstorms which generally produce the most intense hazard to aircraft are

Squall line thunderstorms Signup and view all the answers

A nonfrontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a

Squall line Signup and view all the answers

If there is thunderstorm activity in the vicinity of an airport at which you plan to land, which hazardous atmospheric phenomenon might be expected on the landing approach?

Wind-shear turbulence Signup and view all the answers

Upon encountering severe turbulence, which flight condition should the pilot attempt to maintain?

Level flight attitude Signup and view all the answers

What situation is most conducive to the formation of radiation fog?

Warm, moist air over low, flatland areas on clear, calm nights Signup and view all the answers

If the temperature/dew point spread is small and decreasing, and the temperature is 62°F, what type of weather is most likely to develop?

Fog or low clouds Signup and view all the answers

In which situation is advection fog most likely to form?

An air mass moving inland from the coast in winter Signup and view all the answers

What types of fog depend upon wind in order to exist?

Advection fog and upslope fog Signup and view all the answers

Low-level turbulence can occur and icing can become hazardous in which type of fog?

Steam fog Signup and view all the answers

Convective circulation patterns associated with sea breezes are caused by?

Cool, dense air moving inland from over the water Signup and view all the answers

Which weather phenomenon is always associated with a thunderstorm?

Lightning Signup and view all the answers

The mature stage of a thunderstorm begins with?

The start of precipitation Signup and view all the answers

During a cross-country flight you picked up rime icing which you estimate is 1/2" thick on the leading edge of the wings. You are now below the clouds at 2000 feet AGL and are approaching your destination airport under VFR. Visibility under the clouds is more than 10 miles, winds at the destination airport are 8 knots right down the runway, and the surface temperature is 3 degrees Celsius. You decide to?

Use a faster than normal approach and landing speed Signup and view all the answers

How will frost on the wings of an airplane affect takeoff performance? (Select all that apply)

Frost will disrupt the smooth flow of air over the wing, adversely affecting its lifting capability. Signup and view all the answers

Every physical process of weather is accompanied by, or is the result of, a:

Heat exchange. Signup and view all the answers

What causes variations in altimeter settings between weather reporting points?

Unequal heating of the Earth's surface. Signup and view all the answers

When there is a temperature inversion, you would expect to experience:

An increase in temperature as altitude increases. Signup and view all the answers

The most frequent type of ground or surface-based temperature inversion is that which is produced by:

Terrestrial radiation on a clear, relatively still night. Signup and view all the answers

Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?

Smooth air, poor visibility, fog, haze, or low clouds. Signup and view all the answers

The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to:

Friction between the wind and the surface. Signup and view all the answers

What is meant by the term 'dew point'?

The temperature to which air must be cooled to become saturated. Signup and view all the answers

The amount of water vapor which air can hold depends on the:

Air temperature. Signup and view all the answers

Clouds, fog, or dew will always form when:

Water vapor condenses. Signup and view all the answers

What are the processes by which moisture is added to unsaturated air?

Evaporation and sublimation. Signup and view all the answers

Which conditions result in the formation of frost?

The temperature of the collecting surface is at or below the dew point of the adjacent air and the dew point is below freezing. Signup and view all the answers

The presence of ice pellets at the surface is evidence that there:

Is a temperature inversion with freezing rain at a higher altitude. Signup and view all the answers

What measurement can be used to determine the stability of the atmosphere?

Actual lapse rate. Signup and view all the answers

What would decrease the stability of an air mass?

Warming from below. Signup and view all the answers

What is a characteristic of stable air?

Stratiform clouds. Signup and view all the answers

When warm, moist, stable air flows upslope, it:

Produces stratus type clouds. Signup and view all the answers

If an unstable air mass is forced upward, what type of clouds can be expected?

Clouds with considerable vertical development and associated turbulence. Signup and view all the answers

What feature is associated with a temperature inversion?

A stable layer of air. Signup and view all the answers

What is the approximate base of the cumulus clouds if the surface air temperature at 1,000 feet MSL is 70°F and the dew point is 48°F?

6,000 feet MSL. Signup and view all the answers

At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82°F and the dew point is 38°F?

10,000 feet AGL. Signup and view all the answers

What are characteristics of a moist, unstable air mass?

Cumuliform clouds and showery precipitation. Signup and view all the answers

What are characteristics of unstable air?

Turbulence and good surface visibility. Signup and view all the answers

A stable air mass is most likely to have which characteristic?

Poor surface visibility. Signup and view all the answers

The suffix 'nimbus,' used in naming clouds, means:

A rain cloud. Signup and view all the answers

Clouds are divided into four families according to their:

Height range. Signup and view all the answers

An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 knots or more, is referred to as:

A lenticular cloud. Signup and view all the answers

Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as:

Standing lenticular clouds. Signup and view all the answers

What clouds have the greatest turbulence?

Cumulonimbus. Signup and view all the answers

What cloud types would indicate convective turbulence?

Towering cumulus clouds. Signup and view all the answers

One of the most easily recognized discontinuities across a front is:

A change in temperature. Signup and view all the answers

One weather phenomenon which will always occur when flying across a front is a change in the:

Wind direction. Signup and view all the answers

Steady precipitation preceding a front is an indication of:

Stratiform clouds with little or no turbulence. Signup and view all the answers

Possible mountain wave turbulence could be anticipated when winds of 40 knots or greater blow:

Across a mountain ridge, and the air is stable. Signup and view all the answers

Where does wind shear occur?

At all altitudes, in all directions. Signup and view all the answers

When may hazardous wind shear be expected?

In areas of low-level temperature inversion, frontal zones, and clear air turbulence. Signup and view all the answers

A pilot can expect a wind-shear zone in a temperature inversion whenever the wind speed at 2,000 to 4,000 feet above the surface is at least:

25 knots. Signup and view all the answers

One in-flight condition necessary for structural icing to form is:

Visible moisture. Signup and view all the answers

Study Notes

Frost Effects on Airplanes

Frost disrupts smooth airflow over airplane wings, affecting lift capability negatively.
Even minimal frost can prevent aircraft from taking off at standard speeds, leading to potential safety risks.

Weather Processes

All weather phenomena stem from heat exchange related to unequal heating of the Earth's surface.
The presence of temperature inversions leads to temperature increases with altitude, typically associated with stable atmospheric conditions.

Altimeter Settings

Variations in altimeter settings are primarily caused by unequal heating of the Earth's surface, which impacts pressure differences across locations.

Temperature Inversions

Temperature inversions lead to poor visibility, as they trap moisture, fog, and haze in lower atmospheric layers.
The most common type of ground-based inversion occurs due to terrestrial radiation on clear, windless nights.

Humidity and Dew Point

Dew point is the temperature at which air must be cooled for saturation to occur.
The ability of air to hold water vapor increases with temperature; thus, warmer air can sustain more moisture.

Cloud Formation

Clouds form when water vapor condenses, typically at 100% relative humidity.
Frost forms specifically when the collecting surface's temperature is below the dew point and freezing conditions exist.

Atmospheric Stability and Cloud Types

Stable air results in stratiform clouds, which have smooth air and poor visibility.
Unstable air, on the other hand, leads to significant vertical cloud development, turbulence, and cumulonimbus clouds.

Weather Fronts

Abrupt changes in temperature, humidity, and wind direction often occur across weather fronts, signifying shifts in the air mass characteristics.
Steady precipitation associated with frontal systems is derived from stratiform clouds.

Wind Shear and Turbulence

Wind shear can occur at various altitudes and is often intensified during temperature inversions or frontal passages.
Potential for mountain wave turbulence arises when strong winds intersect stable air over mountainous terrain.

Structural Icing

For structural icing to occur, visible moisture and temperatures below freezing at the point of moisture contact are required.
Freezing rain presents the highest risk for rapid ice accumulation on aircraft surfaces.

Cloud Characteristics and Implications

Lenticular clouds indicate potential strong winds and are often mistaken for static formations.
Cumulonimbus clouds are linked to severe turbulence and demonstrate the extremes of unstable air conditions.

Summary of Key Metrics

Cloud bases can be roughly estimated using dew point and surface temperature differentials, typically yielding values around 4,000 to 10,000 feet MSL depending on specific temperature conditions.
The suffix "nimbus" in cloud names designates rain-producing clouds, indicating precipitation potential.

Visibility and Precipitation Dynamics

Stratiform clouds offer steady but less turbulent precipitation, whereas cumuliform clouds can produce significant weather variability, including showers and turbulence.
Poor surface visibility is often associated with stable atmospheric conditions typical of stratiform cloud formations.### Cumulonimbus Cloud Formation
Cumulonimbus clouds require unstable, moist air, an initial lifting action, and sufficient water vapor for formation.
An unstable lapse rate is essential for thunderstorm development.

Thunderstorm Life Cycle Stages

Cumulus Stage: Characterized by continuous updrafts; development of downdrafts signals transition to mature stage.
Mature Stage: Begins with precipitation; all thunderstorm hazards peak during this stage.
Dissipating Stage: Predominantly features downdrafts and rapid storm decay.

Thunderstorm Characteristics

Squall line thunderstorms present the most severe hazards to aircraft; they are nonfrontal, narrow bands of active storms.
Thunderstorms cause wind-shear turbulence, a hazard that can be encountered far from the storm.

Flight Safety in Thunderstorms

Pilots should maintain a level flight attitude to manage severe turbulence and minimize airframe stress.
Anticipate wind-shear effects when landing near thunderstorm activity.

Fog Formation

Radiation Fog: Forms in moist, warm air over low, flat areas on clear, calm nights due to high relative humidity.
Advection Fog: Occurs when moisture-laden air moves over colder surfaces, commonly along coastlines during winter.
Wind plays a crucial role in the formation of advection and upslope fog, enhancing their intensity and persistence.

Weather Hazards

Low-level turbulence and icing risks are significant in steam fog, which forms over warm ocean waters in winter.
Lightning is a consistent phenomenon with thunderstorms, while presence of heavy rain or hail is not guaranteed.

Cross-Country Flight Considerations

When encountering ice accumulation on the aircraft, it is critical to approach landing with a higher-than-normal airspeed to compensate for increased weight and drag.
Icing can significantly affect flight performance, necessitating adjustments in landing approach speed and configuration.

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Description

This quiz focuses on the impact of weather conditions, specifically frost, on airplane takeoff performance. Understanding how frost affects wing aerodynamics is crucial for pilots and aviation professionals. Test your knowledge on this essential topic.