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CPL Met > Met Lesson 2 > Flashcards

Met Lesson 2 Flashcards

1
Q

ISA Environmental Lapse Rate

A

+ 15°C, with a lapse rate of -1.98°C/1000ft

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2
Q

Dry Adiabatic Lapse Rate

A

3°C/1000ft

Never changes

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3
Q

Saturated Adiabatic Lapse Rate

A

1.5°C/1000ft
Never changes
Dew point temperature has been reached
Latent heat is released during condensation

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4
Q

Calculating Environmental Lapse Rate

A

ELR = (Change in temperature)/(Change in height)

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5
Q

Unstable Atmospheres

A

A lapse rate > 3°C/1000ft

Produce towering cumulus if the air is humid and the air parcel reaches dew point

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6
Q

Stable Atmospheres

A

A lapse rate < 1.5°C/1000ft

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7
Q

Conditionally Stable

A

Air so dry it cannot form clouds

Eg. A parcel of 13°C air in a 14°C atmosphere will not rise

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8
Q

Conditionally Stable or Unstable

A

Air that resists an upsetting tendency until it becomes saturated and then, due to the smaller lapse rate, continues to rise by itself
A lapse rate in between 3°C and 1.5°C/1000ft can either be stable or unstable
Stable when dry
Unstable when saturated

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9
Q

The Adiabatic Process

A

Heated air expands and becomes lighter due to a lower air density than the surrounding/ambient air
The rising air cools and the overall temperature inside the parcel reduces

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10
Q

Air Expansion

A

Expansion cools a gas

Rising air cools adiabatically due to expansion

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11
Q

Air Compression

A

Compression heats a gas

Subsiding air will warm adiabatically

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12
Q

Actual Environmental Lapse Rate (ELR)

A

The vertical temperature profile for the atmosphere over a given point at a specific time during the day
Varies from day to day

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13
Q

Stability

A

The ability of the air to resist any upsetting tendency

Atmospheric stability depends upon the ELR

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14
Q

Absolute Stability

A

A parcel of air that is forced to rise, will sink back when the lifting force is removed

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15
Q

Absolute Instability

A

The inability of air to resist an upsetting tendency even after the removal of the upsetting force
Associated with steep ELRs

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16
Q

High Level Clouds

A 
Cirrus (Ci)
Cirrocumulus (Cc)
Cirrostratus (Cs)
Can create a halo effect
Light to moderate turbulence
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17
Q

Middle Level Cloud

A

Altocumulus (Ac)
Altostratus (As)
If thick, intermittent or continuous rain or snow is common
Can produce virga
Risk of icing: moderate rime and clear ice in the lower levels

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18
Q

Low Level Cloud

A

Cumulus (Cu)
Stratus (St)
Stratocumulus (Sc)
Nimbostratus (Ns)

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19
Q

Stratus

A 
Cloud ceiling very low
Cloud base often ragged/diffused
Poor visibility
VFR flying difficult or impossible
High ground, hills and mountains may be obscured
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20
Q

Nimbostratus

A

Heavy continuous rain

definite risk of icing: moderate rime ice, clear ice more probable in the lower levels

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21
Q

Cumulonimbus (CB)

A

Develops from normal cumulus due to any lifting mechanism with a deep unstable atmosphere
Heavy showers, lightning, squalls at the surface, severe to extreme turbulence
Risk of icing: dangerous clear ice likely

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22
Q

Reporting Cloud Cover

A

FEW: 1 - 2 Oktas
SCT: 3 - 4 Oktas
BKN: 5 - 7 Oktas
OVC: 8 Oktas

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23
Q

Cloud Ceiling

A

Height AGL of BKN or OVC cloud

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24
Q

Cloud Base

A

The bottom of any amount of cloud

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25
Q

Types of Precipitation

A 
Drizzle
Rain
Showers
Hail
Snow
Virga
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26
Q

Intensity of Precipitation

A

Light (-)
Moderate
Heavy (+)

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27
Q

Continuity of Precipitation

A

Showers (convective cloud - TCu or CB): Short duration
Intermittent: Short breaks
Continuous (Ns): Periods longer than an hour without breaks

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28
Q

Virga

A

Falling moisture that evaporates before reaching the ground

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29
Q

Cirrus Cloud

A

Forms ice crystals and therefore has no precipitation

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30
Q

Cirrostratus

A

Prevents sun rays from increasing the daytime temperature significantly

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31
Q

Wind

A

The horizontal movement of air

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32
Q

Pressure Gradient

A

The PGF is the ‘initiating force’ by initiating the movement from a high to a low

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33
Q

Isobar Spacing

A

Indicates wind strength

If the isobars are closer the wind is faster and stronger due to the larger pressure differential

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34
Q

Gradient Wind

A

Blows parallel to the isobars

Gradient wind = PGF + coriolis force

35
Q

Coriolis Force

A

Is the deviating or backing force
The air appears to be turning to the left in the Southern Hemisphere due to the Earths rotation eastwards
Weakest at the equator and strongest at the poles
Increased speed = stronger coriolis force

36
Q

Surface Wind

A

Is gradient wind affected by the friction of the Earths surface
Up to 3,000ft AGL

37
Q

Gradient Wind Verus Surface Wind

A

Surface wind veers more as the coriolis force reduces due to the reducing wind speed
Veers 30 degrees over land compared to the gradient wind
Veers 10 degrees over the sea compared to the gradient wind

38
Q

Highs

A

Anti-cyclones

Rotates anti-clockwise in the Southern Hemisphere

39
Q

Ridge

A

Isobars stretching out from a high

40
Q

Weather Associated with a High

A

Subsiding air is stable and clouds tend to disperse
Subsidence inversions
- may trap impurities and lead to poor visibility
In summer: fine but hazy
Clear nights: radiation fog due to maximum terrestrial radiation

41
Q

Weather Associated with a High Over Land Versus Sea

A

Clear and dry when over land

Over the coast higher humidity may produce stratiform clouds with rain

42
Q

Low

A

Depression
Clockwise rotation
Air flows into a low pressure system

43
Q

Trough

A

Isobars extending out from a low and forming a ‘valleyt’

44
Q

Weather Associated with a Low

A

Rising air will cool
Cloud will tend to form
Large Cu, Cb, Ns cloud depending upon stability
Rain and heavy showers
Turbulence
Good visibility (convection disperses the impurities)

45
Q

Buy Ballot’s Law

A

If facing your back into the wind the low pressure system will be to your right

46
Q

Col Area

A

Area of almost constant pressure between two highs and two lows
Isobars bending away from the centre

47
Q

Weather in a Col

A

Wind light and variable
Possible fog in winter
High temps in summer may lead to thunderstorms

48
Q

Veering

A

Increasing number or clockwise

49
Q

Backing

A

Decreasing number or anti-clockwise

50
Q

Surface Friction

A

Due to uneven and different types of terrain

51
Q

Winds affected by Surface Friction

A

Speed increases with height (less friction)
Up to about 3000ft AGL
Wind direction veers with decreasing height

52
Q

Strength of the Wind Affected by Surface Friction

A

Over land surface wind is one third of the original gradient wind speed
Over water surface wind is two thirds of the original gradient wind speed

53
Q

Right Drift

A

Occurs when you are right of track

54
Q

Left Drift

A

Occurs when you are left of track

55
Q

Lowest Wind Speed

A

Around dawn

At night air is cool and friction is max resulting in calm winds

56
Q

Maximum Wind Speed

A

Around 3pm

Instability of the air with convection currents in the afternoon results in a stronger surface wind

57
Q

Diurnal Variations in Wind Speed and Direction: Night to Day

A

Surface wind increases

The direction backs (anti-clockwise)

58
Q

Diurnal Variations in Wind Speed and Direction: Day to Night

A

Surface wind decreases

The direction veers (clockwise)

59
Q

Squalls (SQ)

A

Ahead of convective clouds and CB
Outflow of cold air
Down-draughts
Gust fronts

60
Q

Line Squalls (LSQ)

A

A band of intense thunderstorms

61
Q

Gust (G)

A

A sudden increase in wind speed of more than 10kts and lasting for only a few seconds

62
Q

Seabreeze

A

Daytime
Occurs about 1000ft AGL
The sun heats the ground faster than the water
The hot air rises over the land
Cooler air moves in from the sea to replace it
Strongest in the mid-afternoon

63
Q

Land Breeze

A

Night
The sea heats up the air
Cooler air from the land replaces the rising air over the water (lower pressure)
Strongest just after sunrise

64
Q

Thermals

A

Temperature versus dew point split could indicate possible thermals
Cause the undershoot/overshoot affect

65
Q

Pilot Actions Whilst Flying Through Thermals

A

Control airspeed
Divert if necessary
Delay for cooler temperatures
Increase the approach speed within the recommended safety margin
Control/capture IAS while maintaining the approach path
Maintain best ROC airspeed

66
Q

Dust Devils

A

Short lived and localised
Only a few metres in diameter
The air and surface is dry
Large temp/dew point split causes the ground to be heated maximally
Visible only due to dust, sand and leaves

67
Q

Dust Storms

A

Moderate to strong winds
Instability
<1000m visibility

68
Q

Katabatic Wind

A

Night or in the early morning
Land loses heat by terrestrial radiation
Gravity pulls the cooler air down the slope

69
Q

Anabatic Wind

A

Daytime, strongest at 3pm
The sun heats the mountain slopes
The hot air rises
Cooler air flows up the slope to replace it
Weaker than katabatic wind as it is fighting gravity

70
Q

Mountain Wave Requirements

A

A mountain greater than or equal to 1000ft
A wind perpendicular to the mountain greater than or equal to 20 - 25kts
A stable layer above the mountain (unstable below)

71
Q

Windward

A

Upwind side of the mountain

72
Q

Leeward

A

Downwind side of the mountain

73
Q

Mountain Wave Turbulence

A

Significant turbulence in the lee side

Down draughts and rotor zones below the crest

74
Q

The Föehn Effect

A

Moist air is forced up against a mountain and creates orographic lifting
The air cools to dew point and cloud forms
The rain falls on the upwind side and the moisture content reduces
The air then descends and warms adiabatically on the lee side with a higher cloud base

75
Q

The Föehn Wind

A

The föehn effect causes a warm, dry wind on the lee side of the mountain

76
Q

Requirements for a Low Level Jet

A

Strong surface (radiation) inversion
High pressure system approaching from the west
North-south mountain range
Subsidence inversion on top preventing the air from flowing over the mountain

77
Q

The Low Level Jet

A

A strong southerly wind along the mountain range
Located over a plain and to the west of a mountain range
Usually below 3000ft AGL

78
Q

Characteristics of a Low Level Jet

A

Strongest in the early mornings as it is colder
Most prevalent in winter with long cold nights
Produces a wind speed of up to 70kts
Usually southerly winds
Strong windshear and turbulence
Disperses when the sun heats the surface inversion

79
Q

Altocumulus lenticularis

A

A stationary cloud formed at or above the crest on the downwind side of a mountain when mountain waves are present if there is sufficient moisture in the air

80
Q

Kelvin-Helmholtz Wave Cloud

A

Clouds get their appearance because the top layer of air moves faster than the lower layer
The top layer gets scooped into a wave-like structure
Indication of severe vertical windshear

81
Q

Dangers of Mountain Waves

A

Updraughts (hypoxia/altitude bust)
Downdraughts (exceed a/c climb capability)
Rotor zones (exceed aileron roll rate)

82
Q

Abnormal Throttle Position

A

Occurs with windshear
Aircraft decreasing in altitude
Pitch the nose up (raise attitude)
Possible stall and decreased speed
Increased power
Leads to decreasing altitude in a full power aircraft seeting
Same can occur when increasing in altitude

83
Q

Pilot Actions When Facing Mountain Waves

A

Fly 1000ft above the crest of the mountain
If heading upwind towards the mountain on the lee-side, cross the ranges at an angle of 30-45 degrees to allow for a faster escape

CPL Met (4 decks)

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