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ATPL > Meteorology > Flashcards

Meteorology Flashcards

1
Q

What’s the percentage of N2 in the atmosphere?

A

78%

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2
Q

What’s the percentage of O2 in the atmosphere?

A

21%

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3
Q

What’s the percentage of CO2, O3 and other gases in the atmosphere?

A

1%

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4
Q

Which atmospheric layer is ozone most prevalent in?

A

Upper Stratosphere

50,000ft to 100,000ft

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5
Q

Ozone absorbs _______ radiation. This causes the temperature to _____.

A

Ultra-violet

rise

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6
Q

Maximum heating of the ozone layer occurs at which altitude?

A

160,000ft

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7
Q

What is the relationship between pressure, volume and temperature in the atmosphere?

A

PV=RT

Where R is the gas constant

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8
Q

What is density in terms of pressure and temperature?

A

density = P/RT

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9
Q

At constant temperature, if pressure increases, density _________

A

increases

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10
Q

At constant pressure, if temperature increases, density _______

A

decreases

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11
Q

Warm air ______, cold air ______.

A

Rises

Sinks

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12
Q

What is the average pressure of the atmosphere at sea level?

A

1013.25 hPa

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13
Q

°C → K

A

+ 273

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14
Q

What is the average temperature at sea level?

A

15°C

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15
Q

What is the average air density at sea level?

A

1225gm/m3

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16
Q

At constant temperature and pressure, moist air is ____ dense than dry air.

A

Less

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17
Q

As altitude increases, pressure and density reduce at a _____ rate in cold air than in warm air.

A

Higher

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18
Q

A warm air mass means _____ pressure aloft.

A

High

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19
Q

A cold air mass means ____ pressure aloft.

A

Low

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20
Q

What is standard pressure at 10,000ft?

A

700mb

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21
Q

What is standard pressure at 18,000ft?

A

500mb

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22
Q

What is standard pressure at 30,000ft?

A

300mb

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23
Q

From sea level to 10,000ft, at what rate does pressure decrease with altitude.

A

1mb per 27ft

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24
Q

50% of atmospheric mass is in the bottom _____ft of the troposphere.

A

20,000ft

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25
Q

90% of the water vapour in the atmosphere is contained in the _________.

A

Troposphere

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26
Q

In which section of the atmosphere is the ozone layer.

A

The Stratosphere

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27
Q

Describe the temperature changes in the atmosphere as altitude increases.

A

15°C at sea level

Decrease at -1.98 per 1000ft till tropopause -56.5°C

Increase till stratopause 0°C

Decrease above stratopause

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28
Q

The tropopause height is greater and the tropopause is colder at the _______

A

Equator

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29
Q

At the poles the tropopause is ______ft and ____°C

A

26,000ft

-45°C

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30
Q

At the equator the tropopause is ______ft and ____°C

A

52,500ft

-75°C

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31
Q

At mid-latitudes the tropopause is ______ft and ____°C

A

36,000ft

-56°C

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32
Q

The tropopause heights vary in the mid-latitudes - _____ in summer and _____ in winter.

A

higher

lower

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33
Q

What is the ISA environmental lapse rate of temperature in the troposphere?

A

-1.96°C per 1000ft

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34
Q

What is QFE?

A

Altimeter pressure setting to give height above station.

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35
Q

What is QNH?

A

Altimeter subscale setting to give altitude above MSL.

(QFE adjusted down to MSL using ISA lapse rate)

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36
Q

What is QFF?

A

QFE adjusted to MSL using actual station temperature (not ISA)

Used for met reports and isobars

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37
Q

What is QNE?

A

Touchdown height if the standard setting (1013mb) is used.

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38
Q

To fly at a certain height above an airfield, what pressure setting should be used?

A

QFE

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39
Q

To fly at a certain altitude above MSL, what pressure setting should be used?

A

QNH

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40
Q

To fly at a flight level (e.g FL65) which pressure setting should be used?

A

1013mb

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41
Q

There is approximately ____% height difference for every ____°C temperature deviation from ISA.

A

4%

10°C

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42
Q

For an airfield above MSL on a hot day, is QNH higher or lower than QFF?

A

Higher

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43
Q

For an airfield below MSL on a hot day, is QNH higher or lower than QFF?

A

lower

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44
Q

When the temperature is low, the true altitude will be _______ than indicated.

A

lower

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45
Q

What is the density altitude lapse rate?

A

120ft per °C temperature deviation

46
Q

1 cal is the amount of heat energy required to…….

A

Raise the temperature of 1 gm of water by 1°C

47
Q

What is the specific latent heat of water?

A

1.0

48
Q

What is sublimation?

A

The conversion of solid to gas (or vice versa) skipping the liquid phase.

49
Q

A change of state _____ or ______ energy

A

Releases

Absorbs

50
Q

The sun’s radiation heats the _____. The earth heats the atmosphere by ______, _______ and _______.

A

Earth

Radiation, Conduction and Convection.

51
Q

The percentage of radiation absorbed is dependent on the _______ and _______.

A

Type of surface

The angle of arrival of the radiation.

52
Q

What is advection?

A

The horizontal movement of air transfering heat.

53
Q

When do minimum surface temperatures occur?

A

30 minutes after sunrise

54
Q

When do maximum surface temperatures occur?

A

2 to 3 hours after mid-day

55
Q

Cloud cover _______ the diurnal variation of surface temperature.

A

Reduces

56
Q

ISA temp is -56.5°C above what height?

A

FL360

57
Q

By volume, what percentage of air in the lower troposphere is water vapour?

A

0 - 5%

58
Q

Half the mass in the atmosphere is found in the lowest ___km.

A

5km

59
Q

What is the SVP?

A

Saturation Vapour Pressure

The water vapour is at a high nough pressure to push water molecules back into the liquid at the same rate as they escape.

60
Q

What does the saturation vapour pressure depend on?

A

Temperature and the evaporating surface.

61
Q

Warm air can hold ____ water vapour than cold air.

A

more

62
Q

What does absolute humidity measure?

What does specific humidity measure?

A

mass of water vapour per unit volume of air

mass of water vapour per unit mass of air

63
Q

In ISA conditions the mass of water the air can hold _______ with height.

A

decreases

64
Q

What are the 3 indicators used to describe the saturation of the air?

A

Relative humidity

Dew point

Wet bulb temperature

65
Q

Increasing the temperature will ______ the relative humidity.

A

decrease

66
Q

What is the dew point?

A

The temperature at which cloud or dew forms

67
Q

The dew point spread indicates _______ ________. It tells you roughly ___ ______ ___ ___ __.

A

relative humidity

how moist the air is

68
Q

The wet bulb temperature lies between _______ and ____.

A

dew point

outside air temperature

69
Q

More water vapour means ____ latent heat energy.

A

more

70
Q

What is the equipment that measures actual environmental lapse rate called?

A

radio sonde

71
Q

What does adiabatic mean?

A

No energy lost or gained by the system

72
Q

What is the DALR?

A

Dry adiabatic lapse rate

3º per 1000ft

73
Q

What is the SALR?

A

Saturated adiabatic lapse rate

1.8º per 1000ft

74
Q

What is meant by stable and unstable air?

A

Stable will sink down again after rising

unstable will continue to rise

75
Q

When the ELR is greater than the DALR, is the air stable?

A

No

76
Q

When the ELR is less than the SALR is the air stable?

A

yes

77
Q

If the ELR is between the SALR and the DALR, the air is stable if _____ and unstable if ______.

A

dry

saturated

78
Q

What rate does the wet bulb temperature fall at?

A

SALR

79
Q

What are the 5 main convection triggers?

A

Orographic

Thermal

Frontal convergence

Non-frontal convergence

Low level turbulence

80
Q

The more moisture in the air the _______ the cloud base and the _______ the tops.

A

lower

higher

81
Q

What are the two effects of surface heating?

A

low level turbulence

convective cloud

82
Q

How do turbulence cloud layers at night compared to those at day?

A

deeper, denser cloud

83
Q

What are the 4 conditions which cause temperature inversions?

A

fronts

surface cooling

subsidence in stable air masses

above turbulence layers

84
Q

How are temperature inversions cleared?

A

heating from below

e.g. daytime heating of land or new air mass being brought in

85
Q

At a cloudbase the _____, ______ and _____ are equal.

A

Dew point

wet bulb

dry bulb

86
Q

Name the force that tries to move air from high to low pressure regions.

It acts _________ to the isobars.

A

Pressure gradient force

perpendicular

87
Q

In the northern hemisphere the coriolis force makes moving air turn _____

A

right

88
Q

Geostrophic wind blows along the _______. In this condition the _____ ______ force and ________ force are equal.

A

isobars

pressure gradient

coriolis

89
Q

What does Buys Ballot’s law state about wind and pressure in the northern hemisphere?

A

If you stand with your back to the wind in the northern hemisphere, low pressure is on your left

90
Q

In which direction do winds circle a low pressure area in the northern hemisphere?

A

anti-clockwise

91
Q

The closer the isobars, the ________ the wind.

A

stronger

92
Q

How many degrees N/S of the equator is the geostrophic wind scale useless?

A

10º

93
Q

For the same isobar spacing, geostrophic wind speed is ______ nearer the equator.

A

higher

94
Q

Geostrophic wind speeds are ______ at altitude.

A

higher

95
Q

The gradient wind is the geostrophic wind modified by _________ _____.

A

centrifugal force

96
Q

Why is the gradient wind, ‘high around a high’?

A

because centrifugal force and pressure gradient force are acting in the same direction

97
Q

Why is the gradient wind, ‘low around a low’?

A

Because the centrifugal force is opposing the pressure gradient force

98
Q

Between which altitudes is Ozone a potential danger?

A

40000 to 75000ft

99
Q

Ozone is usually destroyed by the __________ process

A

pressurisation

100
Q

Dedicated cosmic radiation monitoring equipment must be carried on aircraft operating above _____ft

A

49 000ft

101
Q

Low humidity creates the same symptoms as ________

A

ozone poisoning

102
Q

Why is cabin humidity so low?

A

Low humidity of bleed air and humidifiers are expensive to run

103
Q

Very ___ temperatures increase the susceptibility to hypoxia

A

low

104
Q

Surface friction is greatest over ____ at _____ when the air is coldest and densest.

A

land

night

105
Q

Surface friction is least during the ____ when the air is warmer and less dense

A

day

106
Q

Where are jetstreams found?

A

air mass boundaries

107
Q

In winter jetstreams have ______ speed and are closer to the _______.

A

faster

equator

108
Q

When crossing the jet core what happens to the outside air temperature?

A

Remains constant

109
Q

Which jet stream is connected with a surface front system?

A

Polar front jet stream

110
Q

Where is the core of the Polar front jet stream found?

A

In the tropical air mass

111
Q
A

ATPL (5 decks)

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