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Met > Met Chapter 1 > Flashcards

Met Chapter 1 Flashcards

1
Q

In the ISA, between 11km and 20km altitude, the temperature laps rate is?

A

Isothermal

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2
Q

Why is there a lack of weather in the Stratosphere?

A

The isothermic or inversion conditions in the stratosphere create a physical barrier to further the vertical development of clouds.

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3
Q

Stevenson Screen

A

Kept 4ft (1.2m) off the ground, Slats to prevent sunlight and heat radiation affecting the instruments, door always opens to the closest pole. Used to measure temperature and dew point

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4
Q

Height of the troposphere

A

36,060

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5
Q

Height of the stratosphere

A

36,000

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6
Q

Height of the mesosphere

A

164,000

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7
Q

Height of the thermosphere

A

280,000

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8
Q

Gasses which make up the atmosphere

A

Nitrogen - 75%
Oxygen - 21%
Other gases 1%

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9
Q

What percentage of the atmospheres water vapour is found in the troposphere

A

99%

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10
Q

What is the temp laps rate in the troposphere

A

2 degrees c per 1000 ft

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11
Q

Average height of the tropopause according to ISA

A

11km average
8 - 10 km over the poles
16 - 18 km at the equator

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12
Q

What level is the ozone layer found

A

20 - 30 km

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13
Q

What makes the stratosphere desirable to fly in?

A

Cloud formations are rare due to lack of water Vapor and vertical air movement
Above hazards in the troposphere
Engine efficiency

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14
Q

Where is the ozone found and what effects can it have on the aircraft

A

90% within the stratosphere
Ozone is very harmful so needs to be filtered out

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15
Q

ISA conditions at mean sea level

A

15 degrees C
Temp laps rate of 1.98 per 1000ft
Pressure of 1013 at a laps rate of 1 HPA per 27ft
Density 1.225

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16
Q

What is ISA deviation?

A

If the temp is warmer than isa its (+) if its colder its (-)

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17
Q

What is density proportional to ?

A

Pressure/temperature

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18
Q

what is temp is kelvin at 0 degrees Celsius

A

273

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19
Q

What is a radio scond and what does it measure

A

Rises to an altitude of 35km
Records data in its climb at 1.3 second intervals (temp, Humidity, Pressure)
Transmits to VHF radio

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20
Q

What is solar radiation?

A

Short wave, high frequency

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21
Q

What is terrestrial radiation?

A

Long wavelength

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22
Q

What is the ITCZ

A

The tropical convergence zone which is a band of high pressure around the earth which generally lies around the equator

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23
Q

What does solar radiation reaching the earths surface depend on?

A

Absorption (Ozone layer and water Vapour)
Reflection (tops of clouds and earth)
Scattering (particals in the atmosphere)

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24
Q

What is conduction?

A

Energy transfer by contact
Only happens in the bottom thousand feet

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25
Q

Convection?

A

Energy transfer by vertical movement of air
Heated by earths surface
Heat can be transferred to the atmosphere this way!

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26
Q

Advection

A

Horizontal movement of heat
Takes place when the wind is blowing

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27
Q

Turbulence

A

Energy transfer by mixing of air
Air from higher up is mixing with the air lower down making the surface cooler

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28
Q

Latent heat?

A

Energy released or absorbed by a body with out any change in its temperature
When latent heat is released (surrounding atmosphere is warmed)
Vapour to liquid (heat released)

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29
Q

What is sublimation?

A

When a gas is turned directly into a solid missing out a stage

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30
Q

Icolation

A

The angle of direct heating, if at an angle the energy will be spread out not heating as much as if it was direct

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31
Q

When is the Pherihelium

A

4 of jan closest to the sun

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32
Q

Aphelion

A

4 July furthest away from the sun

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33
Q

Solstice

A

22 of December shortest day
21 of June longest day

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34
Q

Equinox

A

When there is equal day and night
21 of march
23 of September

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35
Q

What is a diurnal variation?

A

The variations of surface temp over a 24 hour period.
Subject to the amount of energy from the sun verse the amount of energy received from the earth

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36
Q

When is the coolest temp in a diurnal variation

A

Coolest is 30 min after sunrise

37
Q

What is the most common ground inversion?

A

Nocturnal surface inversion

38
Q

What are the 4 types of inversion and their descriptions

A

Subsidence inversion
Air descending compresses increasing the pressure of the lower atmosphere. The warmer air is the type sinking and trapping the cooler air beneath it creating an inversion.
Turbulence inversion
The air mixing is done vertically and changes the rate in which the air cools relative to its static environment.
Usually occurs a few thousand feet above ground levels
Visible due to trapped pollutants beneath or by a top cloud layer.
Frontal inversion
The hot air is moved over the cooler more dense air. Usually formed between cold and warm fronts
Valley Inversion
Happens in the evening/night and causes the cold air to move down the sides of the valley.
They create katabatibc winds.
Cool air pools in the valleys thus crating an inversion

39
Q

How does a Mercury barometer work

A

The evacuated tube is filled with mercury.
The height of the mercury column is directly proportional to the atmospheric pressure
Measured in inches of mercury

40
Q

Aneroid barometer

A

Reacts to changes in atmospheric pressure by contracting or expanding

41
Q

Barograph

A

Plots pressure readings against a time to give visible data for forecasting

42
Q

Surface pressure chart

A

Shows horizontal variations in pressure
Isobars join places of equal sea level pressure
Usually 2 or 4 HPA apart
Air will always move high to low

43
Q

What is QFF

A

Is actual pressure at sea level corrected for temperature as well

44
Q

What is a ridge

A

Is an extended high pressure

45
Q

What is a trough

A

A though is a valley of low pressure crossing through isobars

46
Q

What does DALR mean and what’s it’s Laps rate

A

When air is less than 100% humidity

3 per 1000 ft
1 per 100

47
Q

What is SALR and what’s it’s laps rate?

A

Saturated adiabatic laps rate
1.8 per 1000ft
0.6 per 100ft

48
Q

What are the 4 states of stability

A

Absolute stability
Absolute instability
Conditional stability
Natural stability

49
Q

What is absolute stability

A

When the parcel of air returns to its original position once the displacement has taken place. The atmosphere is absolutely stable when the DALR (1 per 100m) and SALR (0.6 per 100m) are more than the EALR (0.2 per 100m)

50
Q

What creates very stable atmospheres?

A

Isotherms and inversions

51
Q

Weather in absolute stable conditions

A

Clouds: will be flat or layered (stratiform clouds)
Precipitation: fairly light but could be persistent.
Visibility: poor due to contaminants staying close to the ground
Turbulence: little to none

52
Q

Absolute instability

A

When the ELR is greater than both DALR (1 per 100m) and the SALR (0.6 per 100m)

53
Q

Weather in unstable conditions

A

Clouds: very strong vertical movement creates cumuliform clouds
Precipitation: reasonably intense, large rain and hail tends to fall for a short period of time.
Visibility: generally good, because dust and smoke particles are lifted up.
Turbulence: moderate to severe due to strong vertical movement

54
Q

Conditional instability

A

When the ELR is between the DALR and SALR. During conditional instability saturated air is unstable.

55
Q

Neutral stability

A

Is when the the ELR is the same as DALR
Or
ELR is the same as SALR

56
Q

What are the 3 classifications of turbulence

A

Light
Moderate
Severe

57
Q

What is the light turbulence criteria

A

Caused slight erratic changes in altitude and/or attitude. IAS fluctuates 5 - 15kt.

Occupants may feel a slight strain against seat belts. Unsecured objects may be displaced. Food service may be conducted and little to no difficulty is encountered when walking.

58
Q

Moderate

A

Similar to light turbulence, ISA 15 - 25kt. Causes rapid bumps or jolts without changes in altitude.

Occupants feel definite strains against seat belts. Unsecured objects are dislodged. Food service and walking difficult.

59
Q

Severe turbulence

A

Turbulence causes large abrupt changes in altitude. Aircraft momentarily out of control. ISA fluctuates more than 25kt.

Occupants are forced violently against seat belts. Unsecured objects are tossed around. Food service and walking impossible.

60
Q

What are the 2 types of turbulence

A

Merchanical turbulence. Caused by physical obstructions such as hills mountains and buildings.

Thermal turbulence, caused by air rising due to surface heating and around cloud formations.

61
Q

How high is a friction layer above the surface

A

1KM on average

62
Q

What conditions lead to mountain waves

A

Wind speed at mountain height must be 15 - 20kt
The wind direction must be 30 degrees of the perpendicular range of the hills/mountains.
There must be a layer of marked stability at mountain top height with less stable air above and below

63
Q

What is a micro burst

A

Small scale downdraft produced by a thunderstorm or rain shower. They last about 5 min and are usually less than 4km diameter

64
Q

What effects does wind sheet have on aircraft

A

Negative shear: a reduction in performance and airspeed (dangerous)
Positive shear: an increase in performance and airspeed (causes deviations from intended flight patch and unstable approach)

65
Q

What creates a downburst

A

Strong, active, convective weather

66
Q

What are the common mechanisms for turbulence

A

Convective
Mechanical
Oragrahic
Frontal
Clear air

67
Q

What is a jet stream

A

Have a speed of at least 60kt
Typical dimensions 2000nm long 200nm wide and about 2nm high

68
Q

What is an cup anemometer

A

A way of measuring the wind speed

69
Q

Where is wind measured and using what SI unit

A

Wind is measured in Knots and is measured 10metres above the ground

70
Q

What are the definitions for wind strength

A

Calm - 1kt or less
Gale fore - mean surface wind 34 - 47kt
Storm force - mean surface wind 48 - 63 knots
Hurricane force - mean surface wind more than 64KT

71
Q

What is a gust?

A

A sudden increase of 10kt or more above the average wind speed and lasting less than a minute

72
Q

What is a squall

A

An increase of 10ky or more above average wind speed and lasting more than 1 minute

73
Q

What is a lull

A

A sudden drop in wind speed

74
Q

What are four forces which have a fundamental influence on the strength and direction of the wind

A

Pressure Gradient PG
Coriolis Effect (also referred to as Coriolis Force) CF
Centrifugal Force (not a type of force, but rather direction)
Friction Force (below 1,000 ft - 3,000ft above the surface)

75
Q

What is the Coriolis Effect

A

When a body of air has a faster speed than the earth is moving. Eg earths rotation speed is faster at the equator than the northern hemisphere

76
Q

What is the Coriolis Force equation

A

2 Ω ρ V Sin θ

Ω (Omega)= angular rotation of the earth (radians/sec) ρ (Rho)= density
V = wind speed
θ = latitude

77
Q

What is Coriolis Force proportional to?

A

-Wind speed (faster wind, more deflection)
–Latitude (higher latitude, more deflection)
–Density (greater density, more deflection)

78
Q

How to find wind velocity

A

V = PGF/2 Ω p sinlt

79
Q

Wind speed is

A

–Directly proportional to PGF
–Inversely proportional to density
–Inversely proportional to latitude.
–As latitude decreases, wind speed increases
–At about 5° from equator coriolis force becomes negligible.

80
Q

Where are gradient winds most likely to be found

A

Around curved isobars

81
Q

Where are Geostrophic winds most likely to be found

A

Along straight isobars

82
Q

Sea Breeze

A

• Timing
–Usually begins around 10am and peaks 2-4 pm
• Strength
–Around 10-15kts but can vary
• Extent
–About 25-40km inland and 2-3000’ high
• Cloud
–Cumulus development over the land
• Temperature
–Air over the land is replaced by cold sea air
• Synoptic
–Usually during anticyclone due to weak PGF

83
Q

To form a Fone wind, what prerequisites must be present?

A

–There must be a substantial mountain range
–The wind must be blowing close to right angles to the range
–The approaching air must have a high moisture content

84
Q

Where might mountain waves be reported

A

On a SIGMET

85
Q

What must the wind speed be to be classed as a jet stream

A

Over 60KT how ever they can get to speeds above 350kt (rarely)

86
Q

What are the jet stream names and locations

A

Artic Jet
Polar front jet (50 - 60 degrees North at 30,000ft)
Sub tropical jet (30 - 40 degrees North at 40,000ft)
Tropical easterly jet (over the equator) also called easterly wave
Sub Tropical jet (30 - 40 degrees South at 40,000ft)
Polar front jet (50 degrees south at 30,000ft)

87
Q

What are the jet stream dimensions

A

Dimensions: 2nm deep, 200nm across, 2000nm long – Ratio: 1:100:1000

88
Q

Where is the Clear Air Turbulence (CAT)

A

It is found near the frontal zone, epecially at the high levels on the polar maritime side and just below the core

89
Q

What are the low level jet streams

A

–Nocturnal Jet
–Valley Inversion
–Coastal Jet
–Ahead of cold front

Met (1 decks)

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