6.AB Flashcards for Weather Variations

Questions and Answers

What causes variations in altimeter settings between weather reporting points?

Unequal heating of the earth's surface

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

Convective circulation patterns associated with sea breezes are caused by?

cool, dense air moving inland from over the water

How will frost on the wings of an airplane affect takeoff performance?

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

A temperature inversion would most likely result in which weather condition?

Clouds with extensive vertical development above an inversion aloft 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

What is meant by the term 'dewpoint'?

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 dewpoint of the adjacent air and the dewpoint 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

Moist, stable air flowing upslope can be expected to?

produce 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 degrees F and the dewpoint is 48 degrees 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 degrees F and the dewpoint is 38 degrees 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?

Smooth air 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

The boundary between two different air masses is referred to as a?

front 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

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/dewpoint spread is small and decreasing, and the temperature is 62 degrees 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

Study Notes

Altimeter Settings and Weather Variations

Variations in altimeter settings between weather reporting points are caused by unequal heating of the earth's surface.

Wind Characteristics

Wind direction differences at various altitudes, such as swesterly winds at 5,000 feet vs. southerly surface winds, result from friction between the wind and the surface.

Sea Breeze Circulation

Convective circulation patterns due to sea breezes occur as cool, dense air moves inland from the water when land heats up more than water.

Impact of Frost on Airplane Takeoff

Frost on an airplane's wings disrupts the smooth air flow, negatively affecting lift capabilities during takeoff.

Weather and Heat Exchange

Every weather phenomenon involves an exchange of heat, indicating that heat is a critical factor in all physical weather processes.

Temperature Inversion Effects

Temperature inversions can lead to clouds with extensive vertical development above the inversion layer.

Ground-Based Temperature Inversions

The most common type of ground-based temperature inversion occurs due to terrestrial radiation on a clear night when the ground cools rapidly.

Weather Beneath Inversion Layers

Beneath low-level temperature inversion layers with high relative humidity, smooth air, poor visibility, fog, haze, and low clouds are typical conditions.

Dew Point Definition

Dewpoint is defined as the temperature air must be cooled to in order to reach saturation.

Water Vapor Capacity

The capacity of air to hold water vapor is directly proportional to its temperature.

Condensation and Cloud Formation

Clouds, fog, or dew form whenever water vapor condenses.

Moisture Addition Processes

Evaporation and sublimation are key processes that add moisture to unsaturated air.

Frost Formation Conditions

Frost occurs when the surface temperature meets or falls below the dewpoint of nearby air, and the dewpoint is also below freezing.

Ice Pellets Evidence

The presence of ice pellets at the surface indicates a temperature inversion with freezing rain occurring at a higher altitude.

Atmospheric Stability Measurement

The actual lapse rate serves as a measurement of atmospheric stability. Stability indicates resistance to vertical displacement, while lapse rate reflects temperature changes with altitude.

Factors Reducing Stability

Warming from below decreases the stability of an air mass.

Characteristics of Stable Air

Stable air is characterized by stratiform clouds, contrasting with unstable air, which features cumulus clouds and good visibility.

Moist Air and Cloud Formation

Moist, stable air flowing upslope typically results in stratus-type clouds.

Clouds in Unstable Air Masses

An unstable air mass forced upward produces clouds with significant vertical development and turbulence.

Temperature Inversion Characteristics

A temperature inversion is associated with a stable air layer.

Cloud Base Calculations

The base of cumulus clouds can be estimated using the difference between temperature and dewpoint, adjusted for altitude; for instance, with a temperature of 70°F and dewpoint of 48°F, the cloud base is around 6,000 feet MSL.

Cumuliform Cloud Base Prediction

If surface air temperature is 82°F with a dewpoint of 38°F, the expected base of cumuliform clouds is about 10,000 feet AGL.

Unstable Air Characteristics

A moist, unstable air mass is characterized by cumuliform clouds and showery precipitation.

Attributes of Unstable Air

Unstable air features turbulence and good surface visibility, as lifting motions create turbulence while clearing clouds and pollutants.

Smooth Air in Stable Environments

Stable air masses are likely to result in smooth air conditions due to resistance to lifting motion.

Cloud Classification

Clouds are categorized into four families based on their height range.

Front Characteristics

The boundary between different air masses is termed a front, which is often accompanied by a noticeable temperature change.

Weather Across Fronts

Transitions across a front always entail a change in wind direction.

Steady Precipitation Indicators

Steady precipitation before a front indicates the presence of stratiform clouds and minimal turbulence, typical of stable air conditions.

Radiation Fog Formation

Radiation fog forms in conditions of warm, moist air over low-lying areas during clear, calm nights, as moist air cools to its dewpoint.

Weather Indicators from Temperature/Dewpoint Spread

A small and decreasing temperature/dewpoint spread, with the temperature at 62°F, likely leads to the development of fog or low clouds.

Advection Fog Formation

Advection fog is most likely to form when a warm air mass moves inland from coastal areas during winter.

Wind Dependency for Fog

Both advection fog and upslope fog depend on wind for their formation.

Low-Level Turbulence and Icing Hazards

Steam fog can lead to low-level turbulence and hazardous icing conditions, occurring when cold, dry air moves over warmer water.

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Description

This set of flashcards covers key concepts related to weather variations, including altimeter settings, wind direction discrepancies, and convective circulation patterns. Perfect for students studying meteorology or aviation weather. Test your knowledge and enhance your understanding of atmospheric phenomena.