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ACFTDSP > AVWX > Flashcards

AVWX Flashcards

1
Q

What is the cause of all weather changes?

A

Uneven heating of the Earth’s surface, causing pressure and air density differences.

FAA-H-8083-28, Aviation Weather Handbook

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2
Q

What are characteristics of cold fronts?

A

Cold fronts typically move at approximately the speed of prevailing wind and create lift along leading edge, conducive to cumulous cloud development, medium to heavy precipitation, showery at times.

FAA-H-8083-28, Aviation Weather Handbook

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3
Q

What are characteristics of warm fronts?

A

Warm fronts move at about half of the prevailing wind speed and can be conducive to stratus cloud development, constant light precipitation and low visibilities.

FAA-H-8083-28, Aviation Weather Handbook

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4
Q

What are characteristics of occluded fronts?

A

Occluded fronts can cause weather similar to that of warm fronts and cold fronts. Embedded thunderstorms may be possible.

FAA-H-8083-28, Aviation Weather Handbook

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5
Q

What are characteristics of stationary fronts?

A

Stationary fronts can cause weather similar to cold fronts and be stagnant until the cold front typically moves through the area.

FAA-H-8083-28, Aviation Weather Handbook

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6
Q

Definition of a temperature inversion

A

A layer of warm air above colder air.

FAA-H-8083-28, Aviation Weather Handbook

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7
Q

What causes a surface based temperature inversion and what are the impacts to aircraft operations in the area?

A

A surface-based low-level temperature inversion can be caused by extreme surface cooling under clear skies and light/calm wind conditions can cause poor visibility. Low-level wind shear (LLWS) is possible during climb or descent through the layer of stable air which separates calm air close to the surface from higher wind speed above.

FAA-H-8083-28, Aviation Weather Handbook

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8
Q

What are characteristics of the troposphere?

A

Layer of atmosphere from Earth’s surface to approximately 36,000 feet in the mid latitudes.
Large-scale vertical air motions
Standard lapse rate 2°c/1,000’
50% atmospheric moisture below 6,500’
Most weather occurs

FAA-H-8083-28, Aviation Weather Handbook

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9
Q

What are characteristics of the stratosphere?

A

Layer of the atmosphere which starts at approximately 36,000 feet in the mid latitudes.
Horizontal/stratified air motion
Common location for jet stream
Little or no temperature change with increase in altitude, eventually increasing with altitude around 45-50,000’

FAA-H-8083-28, Aviation Weather Handbook

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10
Q

What are air motions in a low pressure area?

A

Counter-clockwise and rising air, conducive to an unstable atmosphere and cumulous cloud development.

FAA-H-8083-28, Aviation Weather Handbook

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11
Q

What are air motions in a high pressure area?

A

Clockwise and sinking air, conducive to a stable atmosphere and stratus cloud development.

FAA-H-8083-28, Aviation Weather Handbook

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12
Q

What causes cloud development?

A

Temperature and dew point converge (condensation of atmospheric moisture).

FAA-H-8083-28, Aviation Weather Handbook

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13
Q

What atmospheric conditions are conducive to development of cumulous clouds?

A

Low pressure, unstable atmosphere, and a lifting mechanism (surface heating, orographic lifting, frontal (cold) lifting).

FAA-H-8083-28, Aviation Weather Handbook

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14
Q

What atmospheric conditions are conducive to development of stratus clouds?

A

High pressure, stable atmosphere.

FAA-H-8083-28, Aviation Weather Handbook

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15
Q

List types of fog

A

Radiation fog
Advection fog
Upslope fog
Steam fog
Frontal fog

FAA-H-8083-28, Aviation Weather Handbook

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16
Q

What atmospheric characteristics are conducive to thunderstorm (cumulonimbus cloud) development?

A

Sufficient moisture
Unstable atmosphere
Lifting mechanism(s) such as buoyancy (surface heating), orography (rising terrain), and/or frontal lifting (cold or occluded front)

FAA-H-8083-28, Aviation Weather Handbook

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17
Q

What is the difference between an air mass thunderstorm and a steady state (severe) thunderstorm?

A

Air mass = localized, results mostly from surface heating
Steady state = associated with organized surface weather systems (cold fronts, hurricanes)

FAA-H-8083-28, Aviation Weather Handbook

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18
Q

Name and describe the stages of a thunderstorm and which stage presents the greatest hazards?

A

1.Cumulous (continuous updrafts initially build cumulonimbus cloud)
2.Mature (precipitation produces downdrafts, updrafts continue)
3.Dissipating (downdrafts exceed updrafts, cloud collapses)

Greatest hazards exist during mature stage (turbulence, potential severe wind shear, lightning, hail, airframe icing).

FAA-H-8083-28, Aviation Weather Handbook

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19
Q

List all thunderstorm hazards

A

1.Turbulence, potential severe wind shear, microburst
2.Lightning
3.Hail
4.Airframe icing
5.Pressure changes can cause altimeter inaccuracy.

FAA-H-8083-28, Aviation Weather Handbook

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20
Q

What is wind shear?

A

Any sudden change in wind direction and/or speed, particularly when it occurs over relatively short distance in flight. Low-level wind shear (LLWS) occurs below 2,000 feet AGL.

FAA-H-8083-28, Aviation Weather Handbook

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21
Q

What is a microburst?

A

Local wind shear as a result of heavy rain from a cumulonimbus (CB) cloud (thunderstorm).

Downdraft is caused by heavy rain falling, accelerated by its colder temperature than surrounding air. Can be as much as 6,000 fpm and causes horizontal winds as much as 45 knots upon striking the ground, resulting in potential total shear of as much as 90 knots across the microburst.

FAA-H-8083-28, Aviation Weather Handbook

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22
Q

What is a jet stream and how does time of year affect it?

A

High-speed organized band of wind with speeds 50 knots or greater in the vicinity of the tropopause. In the winter, the jet stream is higher speed, lower in height, and further south.

FAA-H-8083-28, Aviation Weather Handbook

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23
Q

What is the definition of potential icing conditions?

A

Visible moisture and temperature 0° Celsius or colder.

Aircraft manufacturers commonly define icing conditions as +10° and colder in visible moisture due to aerodynamic cooling over the wing surface.

FAA-H-8083-28, Aviation Weather Handbook

24
Q

List types of airframe ice

A

Clear
Rime
Mixed

FAA-H-8083-28, Aviation Weather Handbook

25
Q

Describe atmospheric conditions conducive to clear ice

A

0° to -15° Celsius
High water content and large water droplets found in cumulous/cumulonimbus clouds.

FAA-H-8083-28, Aviation Weather Handbook

26
Q

Describe atmospheric conditions conducive to rime ice

A

-25° to -40° Celsius
Low water content and small water particle size found in stratus clouds.

FAA-H-8083-28, Aviation Weather Handbook

27
Q

Describe mixed ice

A

When aircraft accumulates alternating layers of clear and rime depending on the environment.

FAA-H-8083-28, Aviation Weather Handbook

28
Q

What effect does airframe icing have on an aircraft, which type is the most hazardous, and why?

A

Ice affects aircraft controllability by altering airflow over wings, reducing ability to produce lift, and increasing drag. Stall speed may be higher than normal as a result of the change in aerodynamic shape of wings.

Clear ice is the most hazardous, due to its nature to form beyond the heated leading edge of wings, adds considerable weight, and can be difficult to detect visually.

FAA-H-8083-28, Aviation Weather Handbook

29
Q

Describe Clear Air Turbulence (CAT)

A

Turbulence in cloud-free regions not associated with thunderstorms, such as in the vicinity of the jet stream and mountain wave turbulence.

FAA-H-8083-28, Aviation Weather Handbook

30
Q

What is holdover time?

A

Holdover time is the estimated time deicing/anti-icing fluid will prevent the formation of frost or ice and the accumulation of snow on the protected surfaces of an aircraft.

Holdover time begins when the final application of deicing/anti-icing fluid starts and expires when the deicing/anti-icing fluid loses its effectiveness.

§121.629 Operation in icing conditions.

31
Q

Definition of dew point

A

Temperature at which air will become saturated.
Visible moisture (fog) results from saturation.

Lowering air temperature reduces its capacity to hold water vapor.

32
Q

Standard pressure at sea level in inches of Mercury and millibars

A

29.92 Hg / 1013.25 Mb

33
Q

Standard temperature lapse rate

A

2° Celsius per 1,000 feet

34
Q

Standard pressure lapse rate ______ inches Mercury per _______ feet

A

1” / 1,000 feet

35
Q

Coldest time in a 24-hour period

A

Just after sunrise.

Shortly after sunrise, incoming solar radiation received at the Earth’s surface becomes greater than outgoing terrestrial radiation and the Earth’s surface warms.

36
Q

Three basic properties of the atmosphere

A

Temperature, density, and pressure

37
Q

Definition of jet stream

A

Jet streams are relatively narrow bands of strong wind (50 knots or greater) in the upper levels of the atmosphere.

38
Q

Definition of a front

A

A front is a boundary or transition zone between two air masses.

39
Q

Common Sources of Vertical Motion

A

The most common types of vertical motion are orographic effects, frontal lift, and buoyancy.

40
Q

Definition of atmospheric stability

A

Atmospheric stability is the property of the ambient air that either enhances or suppresses vertical motion of air parcels and determines which type of clouds and precipitation will develop. Low pressure = unstable, high pressure = stable

41
Q

Three basic cloud forms

A

Cirriform (Cirrus), cumuliform (cumulous), and stratiform (stratus)

42
Q

Definition of nimbus

A

A cloud producing rain

43
Q

Four significant cloud types

A

Alto cumulous standing lenticular (ACSL)
Cumulonimbus (CB)
Towering Cumulous (TCU)
Cumulonimbus Mammatus (CBMAM)

44
Q

Definition of wind shear

A

Wind shear is the change in wind speed and/or direction.

Wind shear generates turbulence between two wind currents of different directions and/or speeds.

45
Q

Causes of turbulence

A

Turbulence is caused by convective currents (convective turbulence), obstructions in the wind flow (mechanical turbulence), and wind shear.

46
Q

What is convective turbulence?

A

Convective turbulence is turbulent vertical motions that result from convective currents and the subsequent rising and sinking of air.

Convective currents are most active on warm summer afternoons when winds are light.

47
Q

What is mechanical turbulence?

A

Mechanical turbulence is turbulence caused by obstructions to the wind flow, such as trees, buildings, mountains.

Obstructions to the wind flow disrupt smooth wind flow.

The higher the speed and/or the rougher the surface, the greater the turbulence.

48
Q

What is a mountain wave or mountain wave turbulence (MWT)?

A

A mountain wave is an atmospheric wave disturbance formed when stable air flow passes over a mountain or mountain ridge. Mountain waves are a form of mechanical turbulence which develop above and downwind of mountains and may extend 600 miles or more downwind from the mountain range and have been documented up to 200,000 feet and higher.

49
Q

Definition of clear air turbulence (CAT)

A

Clear Air Turbulence (CAT) is a higher altitude (20,000 to 50,000 feet) turbulence phenomenon occurring in cloud-free regions associated with wind shear, particularly between the core of a jet stream and the surrounding air.

CAT frequency and intensity are maximized during winter when jet streams are strongest.

50
Q

At what lowest temperature can water in the atmosphere exist in liquid form?

A

Pure water suspended in the air does not freeze until it reaches a temperature of -40 °C. Surface tension of the droplets inhibits freezing. The smaller and purer the water droplet, the more likely it is supercooled.

51
Q

What is the specific risk associated with Supercooled Large Drops (SLDs)?

A

Supercooled Large Drops (SLDs) are common in freezing rain and freezing drizzle situations.

52
Q

Necessary Ingredients for Thunderstorm Cell Formation.

A

Thunderstorm cell formation requires three ingredients:
1) sufficient water vapor
2) unstable air
3) a lifting mechanism

53
Q

Life cycle (3 stages) of a thunderstorm (cumulonimbus) cell

A

Towering Cumulous
Mature
Dissipating

54
Q

Thunderstorm hazards

A

1.Turbulence, potential severe wind shear, microburst
2.Lightning
3.Hail
4.Airframe icing
5.Pressure changes can cause altimeter inaccuracy.

FAA-H-8083-28, Aviation Weather Handbook

55
Q

What is a downburst? Microburst?

A

Intense downdrafts created by thunderstorm cells that create strong, often damaging winds.

Smaller, shorter-lived downbursts are called microbursts.

ACFTDSP (22 decks)

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