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Army Aviation > Weather > Flashcards

Weather Flashcards

1
Q

Natural Air is:

A

Dry air + Condensation Nuclei + Water Vapor

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2
Q

Troposphere height at equator:

A

ca. 60.000 ft

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3
Q

Troposphere height at the poles:

A

ca. 25.000 ft

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4
Q

3 reasons for the 3-cell theory of circulation:

A
  • Uneven heating of sun
  • Coriolis force
  • Tilt of earth
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5
Q

Low pressure on northern hemisphere rotates _____

A

Counter-clockwise

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6
Q

High pressure on northern hemisphere rotates _____

A

Clockwise

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7
Q

30* - 60* N latitude has primarily ______ winds.

A

Western

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8
Q

Where in the atmosphere does the weather occur?

A

Troposphere

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9
Q

4 types of heat transfer:

A

Radiation
Conduction
Convection
Advection

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10
Q

Where would you find the strongest thermal current?

A

Over land surface during daylight hours

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11
Q

OLR is short for:

A

Observed Lapse Rate

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12
Q

How is heat transfered through radiation:

A

As electromagnetic waves

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13
Q

What is insolation?

A

The radiation comming from the sun to the earth

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14
Q

what is terrestrial radiation?

A

The radiation leaving earth into the space

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15
Q

A layer of air, characterized by increase in temp by altitude is called:

A

Temperature inversion

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16
Q

How is change in pressure depicted on a weather chart?

A

Isobars - Drawn 4 Mb apart

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17
Q

PGF short for

A

Pressure gradient force

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18
Q

PGF is defined as:

A

The rate at which air will accelerate depends on rate at which pressure changes with distance

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19
Q

Strong/Steep pressure gradient force is when:

A

Isobars are closely spaced together and there are stronger winds

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20
Q

Weak/flat pressure gradient force is when:

A

Isobars are separated further apart and the winds are more calm

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21
Q

at a high pressure situation the winds are moving ____ and ____ to the isobars, and ____ and ____ in low pressure situation

A

Clockwise , parallel

Counterclockwise , parallel

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22
Q

In theory, at what altitude stops surface friction?

A

2.000 ft AGL

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23
Q

When below 2.000 ft AGL how is the winds changed when surface friction is applied:

High Pressure:
Low pressure:

A
  • High pressure: The winds diverge out from the center

- Low pressure: The winds converge towards the center

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24
Q

High pressure on northern hemisphere is a (cyclone/anticyclone)

A

Anticyclone

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25
Q

Low pressure on northern hemisphere is a (cyclone/anticyclone)

A

Cyclone

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26
Q

Left crosswind is an indication that you are flying towards:

A

Lower pressure

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27
Q

What is deposition?

A

When a gas goes to solid without being liquid first

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28
Q

What is sublimation?

A

When a solid goes to gas without being liquid first

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29
Q

How is flight performance affected by moisture in the atmosphere

A

Gives less air density which is not good for flying

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30
Q

Adiabatic process is described as:

A

When the temperature of a gas is changed without the addition or deletion of heat energy.
(When air rises og falls and heats/cools because of the pressure changes)

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31
Q

Dry adiabatic lapse rate:

A

3*C/1000ft

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32
Q

Moist adiabatic lapse rate:

A

1.5*C/1000ft

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33
Q

LCL is short for:

A

Lifted condensation level

34
Q

LFC is short for:

A

Level of free convection (when: rising air = ambient air)

35
Q

Water droplets cooled below freezing, while still liquid is called:

A

Supercooled water droplets

36
Q

Air being lifted over a mountain range will cool on the windward side and heat up as it moves downslope on the leeward side. this temperature change is a result of what process?

A

Adiabatic process

37
Q

Level of free convection is what?

A

Where the rising air temperature is the same as the ambient air temperature

38
Q

Level of condensation is what?

A

Rising air temperature is the same as the dew point temperature and clouds are formed

39
Q

If lifting occurs, air with high moisture content tend to be more _____ than dry air (stable/unstable)

40
Q

What conditions should be present to determine if a front i present

A 
Temperature change
Dew point Change
Pressure change (fall then rise)
Wind shift - approx 90*
41
Q

Primal factors affecting how servere a front will be:

A

Slope
Speed
Moisture content
Stability

42
Q

What can you expect to see if a cold front is moving really fast?

A

A squall line

43
Q

Wind blows _____ (from/to) a direction, and a front moves ____ (from/to) a direction?

44
Q

Flight procedure for:

Cold front / squall lines

A

Land and wait

45
Q

Flight procedure for:

Warm / stationary front

A

Prepare for alternate landing location

46
Q

Flight procedure for:

frontal wave

A

Handle each front individually

47
Q

Flight procedure for:

occluded front

A

Avoid the most servere weather which is generally located in an area 100 nm south or 300 nm north of the frontal intersection

48
Q

6 Types of fog:

A 
Radiation fog
Advection fog
Precipitation-induced fog
Upslope fog
Freezing fog
Ice fog
49
Q

What causes radiation fog?

A

Cooling of the air - Radiation cooling (requires a few knots og wind)

50
Q

What causes advection fog?

A

Warm moist air moving over a cold surface (3-9kts wind)

51
Q

What causes Precipitation-induced fog?

A

precipitation from precipitation falling through cool unsaturated air. Usually forms ahead a warm front og behind a cold front

52
Q

What causes upslope fog?

A

Moist, stable air being lifted by sloping terrain

53
Q

What causes freezing fog?

A

When supercooled droplets contact freezing surface

54
Q

What causes ice fog?

A

Extremely cold temperatures and depositions (at around -30*C)

55
Q

4 types of ice.

A

Rime ice
Clear ice
Mixed ice
Frost

56
Q

How is rime ice formed?

A

Formed from small supercooled water droplets

57
Q

How is clear ice formed?

A

Formed from large supercooled water droplets

58
Q

How is Mixed ice formed?

A

Formed as a combination of rime and clear

59
Q

How is frost formed?

A

Formed through the process of deposition where vapor get in contact with a cold surface

60
Q

4 Intensities of icing:

A

Trace
Light
Moderate
Servere

61
Q

Why can icing cause los of airspeed readings?

A

If Pito/static systems get iced

62
Q

What is freezing rain?

A

Forms when rain droplets fall thru a frontal inversion into a layer of air with a subzero temperature. - Mostly seen in warm fronts

63
Q

3 conditions fora thunderstorms to happen:

A

Unstable of conditionally unstable air
High moisture content
Lifting action

64
Q

Air mass thunderstorm i caused by:

A

Surface heating

65
Q

Orographic thunderstorm i caused by:

A

Terrain effects

66
Q

In what front would the chance of thunderstorms be be greatest?

A

In an occlusion

67
Q

3 stages of a thunderstorm building:

A

Cumulus stage
Mature stage
Dissipating stage

68
Q

Regarding thunderstorms the cumulus stage is:

A

When the thunderstorm first starts to build. Updraft - no precipitation

69
Q

Regarding thunderstorms the mature stage is:

A

When precipitation begins and turbulence becomes more servere

70
Q

Regarding thunderstorms the dissipation stage is:

A

Then the cloud starts dissipating - Primarily downdraft

71
Q

What is a microburst?

A

Short-lived powerful downburst associated with convective activity

72
Q

Dry air consists off:

A

Oxygen
Nitrogen
Trace gasses (CO2 etc)

73
Q

What is advection:

A

Horizontal transfer of heat

74
Q

Two types of temperature inversion:

A

Nocturnal and frontal inversion

75
Q

Cause of frontal weather:

A

Lifting warm air over cold air

76
Q

Which front has temperature inversion

A

All of them

77
Q

Winds of either side of a stationary front blows:

A

parallel and opposite

78
Q

When a cold air behind the cold front overtakes the cool air in front of the cold front you get a (cold/hot occlusion)?

A

Cold occlusion

79
Q

Conditions that form fog

A
  • Small t/d change
  • Condensation nuclei
  • Light surface wind
  • Cooling land surface
80
Q

When is a dry microburst most likely to occur

A

Summer at noon under a cumulus with virgo present

Army Aviation (8 decks)

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