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ATPL Theory - Module 1 > Meteorology - The Atmosphere > Flashcards

Meteorology - The Atmosphere Flashcards

The Atmosphere

1
Q

What are the main component gases of the atmosphere in DRY air?

A

Nitrogen 78%
Oxygen 21%
Argon 0.9%
Traces of CO2 and other gases

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2
Q

What are the three gases which play the most important part in weather?

A

CO2
Ozone
Water vapour

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3
Q

Describe water vapour

A

Carries large amounts of latent heat energy
A light, transparent gas
Averages less than 1%, but local concentration can vary from 0% to 4%

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4
Q

Where is most of Earth’s water vapour found?

A

Low altitudes and areas of high temperature

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5
Q

In what form does the Sun’s energy reach the Earth?

A

Short wave radiation

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6
Q

How’s the Sun’s energy reflected back?

A

As long wave radiation

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7
Q

What causes the Greenhouse effect?

A

Carbon Dioxide and water vapour absorbing some of the long wave radiation reflected back from the Sun

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8
Q

Describe the general gas law as a formula. What does R stand for?

A

Pressure x Volume = R x Temperature
A gas constant for the gas or mix of gases we’re dealing with

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9
Q

How is density defined?

A

The mass of a unit volume of a gas

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10
Q

How does density relate to volume in a fixed mass of air?

A

Density is inversely proportional
Volume increases, density reduces

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11
Q

How is pressure defined?

A

A unit of force per area

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12
Q

A Hectopascal is equal to one…

A

Millibar

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13
Q

What’s the average pressure of the atmosphere at sea level in hPa? And in inches of mercury?

A

1013.25 millibars
29.92

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14
Q

What’s the most common type of barometer?

A

A mercury barometer

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15
Q

Describe how an aneroid barometer works

A

Using a closed, evacuated capsule that expands and contracts under changing pressure

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16
Q

What’s a barograph?

A

An aneroid barometer that records changing pressure in graphical form

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17
Q

What are recorded on surface weather charts?

A

Barometric pressures from hundreds of observation stations

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18
Q

How does one get a good overview of pressure distribution on a surface pressure chart?

A

By joining points of equal pressure

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19
Q

What secondary thing do we get from surface weather charts besides seeing pressure distribution easily?

A

An estimation of the wind direction and speed at any given point

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20
Q

What’s the most commonly measured weather parameter?

A

Temperature

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21
Q

What does temperature describe?

A

The kinetic energy or energy of morion, of the gases that make up the air

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22
Q

Name four major atmospheric phenomena which are affected by temperature

A

Rate of evaporation
Relative humidity
Wind speed and direction
Precipitation patterns and types

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23
Q

For calculations in thermodynamics…must be used

A

°A( Absolute temperature) or Kelvin

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24
Q

How does one convert to Kelvin from °C?

A

+273

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25
Q

What are the key temperatures in Fahrenheit?

A

Freezing point of water: 32°F
Boiling point of water: 212°F

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26
Q

How does one convert from °C to F°?

A

T(°C) x 1.8 + 32

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27
Q

How does one convert from Fahrenheit to Celcius?

A

(T(°F) -32) / 1.8

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28
Q

How is density measured in meteorology?

A

Grams per cubic metre

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29
Q

What’s the average temperature at sea level in °C and K?

A

15°C
288K

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30
Q

What’s the correct gas constant for dry air at sea level?

A

1225 g/㎥

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31
Q

What will happen to the msl air density constant if water vapour is present?

A

There will be a lower density for the same conditions of temperature and pressure

32
Q

What’s the sea level density of water vapour?

A

About 760 g/㎥ (over half the density of the dry atmosphere)

33
Q

Air density…with altitude

A

Decreases

34
Q

At roughly what altitude is air density of that of at sea level? And quarter?

A

22,000 ft
40,000 ft

35
Q

T or F
The rate of change of pressure with altitude is linear

A

F

36
Q

How is upper air data usually collected?

A

By a Radiosonde
A balloon with an instrument pack that records temperature, pressure and humidity and radios it back to a ground station

37
Q

How might radar tracking be used in conjunction with a radiosonde?

A

As a means of collecting upper air data

38
Q

Which two atmospheric conditions always reduce with height?

A

Pressure and density

39
Q

How does temperature affect pressure and density?

A

Only the rate at which they fall

40
Q

Pressure and density fall…rapidly in cold air as height increases

A

More

41
Q

In warm air, the pressure aloft is always…

A

Higher

42
Q

What’s the feet per mb at 10,000 ft? And the pressure at ISA?

A

36 ft
700 mb

43
Q

What’s the feet per mb at 18,000 ft? And the pressure at ISA?

A

48 ft
500 mb

44
Q

What’s the feet per mb at 30,000 ft? And the pressure at ISA?

A

72 ft
300 mb

45
Q

How are feet per mb calculated?

A

Feet per hPa = 96T (K) / P(hPa)

46
Q

Pressure is approximately 50% of MSL pressure at…

A

18,000 ft

47
Q

Density approximately 50% of MSL at…

A

22,000 ft

48
Q

Density is approximately 25% of MSL density at…

A

40,000 ft

49
Q

What’s the lowest level of atmosphere called? What are its extremities in feet?

A

The Troposphere
Approx. Ground to 8-16 km

50
Q

How’s the Troposphere characterised?

A

Air cools adiabatically as it rises
Temperature falls as altitude rises until the Tropopause
Almost all weather occurs here

51
Q

At the poles the troposphere is…than at the equator, reaching altitudes of approximately…

A

Lower
8 km

52
Q

Why does temperature decrease with height?

A

In response to the reducing air density/thinner air

53
Q

Which layer occurs above the Tropopause?

A

The Stratosphere

54
Q

Describe the Stratosphere’s composition and temperature characteristics
What are its extremities?

A

The upper two thirds are ozone
The temperature stays constant just above the Tropopause then steadily increases to a maximum at the Stratopause, then reducing again as the atmosphere thins further
16 - 50 km

55
Q

The stratosphere holds about…of the atmosphere’s gases but very little…

A

19%
Water vapour

56
Q

What is above the mesosphere? How else is it known?

A

The thermosphere
The ionosphere

57
Q

What’s above the stratopause?

A

The mesosphere

58
Q

What’s the highest layer of Earth’s atmosphere?

A

The exosphere

59
Q

…% of the mass of the atmosphere lies in the bottom…of the…

A

50%
20,000 feet
Troposphere

60
Q

Why does temperature increase in the ozone layer? From what to what?

A

Heat is produced in the formation of Ozone
From an ISA average of -56.5° to approximately -15°C

61
Q

Describe how ozone is formed

A

Diatomic oxygen absorbs UV radiation with wavelengths less than 240 nm and is split into two oxygen atoms
This is exothermic and results in 2 ozone molecules from every three diatomic oxygen molecules and light to heat conversion

62
Q

What happens to zone when exposed to UV?

A

It absorbs UV with wavelengths up to 290 nm
This UV causes it to decompose into O2 molecules and oxygen atoms
This is exothermic

63
Q

What’s the result of the stratosphere’s temperature profile?

A

Very stable atmospheric conditions
Almost completely clear of clouds/weather

64
Q

How might the stratosphere benefit long distance flight

A

It’s above stormy weather
It has strong steady horizontal winds

65
Q

Why does most commercial flight tend to cruise near the top of the tropopause?

A

Low temperatures and low air density, reducing parasitic drag

66
Q

How does ozone pose a threat to commercial flight? How can this be mitigated?

A

It’s poisonous
By fitting catalytic converters to aircraft aircon, which break the ozone down into oxygen

67
Q

What are the extremities of the mesosphere?

A

50 km to 85 km

68
Q

Why does the mesosphere switch back to cooling with altitude?

A

As air becomes progressively less dense with altitude

69
Q

Where do meteors tend to burn up? Why?

A

In the mesosphere
The gases are thick enough to slow them down

70
Q

Which layers are considered to be the middle atmosphere?

A

The stratosphere and the mesosphere

71
Q

Which layer lies between 85 km and 600 km?
How else is it known?

A

The thermosphere
The upper atmosphere

72
Q

Why does the thermosphere increase in temperature with height?

A

UV and X-ray radiation from the sun heats the atmosphere/exosphere’s molecules as they first make contact

73
Q

What can the extremities of temperature be in the thermosphere?

A

-120°C to 2000°C

74
Q

What’s notable about the high temperatures in the thermosphere?

A

They would still feel cold to the skin as there are so few molecules here

75
Q

What’s the outermost layer of the atmosphere? What are its extremities?

A

The exosphere
600 km to 10,000 km

76
Q
A

ATPL Theory - Module 1 (17 decks)

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