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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
Types of Precipitation
``` Drizzle Rain Showers Hail Snow Virga ```
26
Intensity of Precipitation
Light (-) Moderate Heavy (+)
27
Continuity of Precipitation
Showers (convective cloud - TCu or CB): Short duration Intermittent: Short breaks Continuous (Ns): Periods longer than an hour without breaks
28
Virga
Falling moisture that evaporates before reaching the ground
29
Cirrus Cloud
Forms ice crystals and therefore has no precipitation
30
Cirrostratus
Prevents sun rays from increasing the daytime temperature significantly
31
Wind
The horizontal movement of air
32
Pressure Gradient
The PGF is the 'initiating force' by initiating the movement from a high to a low
33
Isobar Spacing
Indicates wind strength | If the isobars are closer the wind is faster and stronger due to the larger pressure differential
34
Gradient Wind
Blows parallel to the isobars | Gradient wind = PGF + coriolis force
35
Coriolis Force
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
Surface Wind
Is gradient wind affected by the friction of the Earths surface Up to 3,000ft AGL
37
Gradient Wind Verus Surface Wind
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
Highs
Anti-cyclones | Rotates anti-clockwise in the Southern Hemisphere
39
Ridge
Isobars stretching out from a high
40
Weather Associated with a High
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
Weather Associated with a High Over Land Versus Sea
Clear and dry when over land | Over the coast higher humidity may produce stratiform clouds with rain
42
Low
Depression Clockwise rotation Air flows into a low pressure system
43
Trough
Isobars extending out from a low and forming a 'valleyt'
44
Weather Associated with a Low
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
Buy Ballot's Law
If facing your back into the wind the low pressure system will be to your right
46
Col Area
Area of almost constant pressure between two highs and two lows Isobars bending away from the centre
47
Weather in a Col
Wind light and variable Possible fog in winter High temps in summer may lead to thunderstorms
48
Veering
Increasing number or clockwise
49
Backing
Decreasing number or anti-clockwise
50
Surface Friction
Due to uneven and different types of terrain
51
Winds affected by Surface Friction
Speed increases with height (less friction) Up to about 3000ft AGL Wind direction veers with decreasing height
52
Strength of the Wind Affected by Surface Friction
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
Right Drift
Occurs when you are right of track
54
Left Drift
Occurs when you are left of track
55
Lowest Wind Speed
Around dawn | At night air is cool and friction is max resulting in calm winds
56
Maximum Wind Speed
Around 3pm | Instability of the air with convection currents in the afternoon results in a stronger surface wind
57
Diurnal Variations in Wind Speed and Direction: Night to Day
Surface wind increases | The direction backs (anti-clockwise)
58
Diurnal Variations in Wind Speed and Direction: Day to Night
Surface wind decreases | The direction veers (clockwise)
59
Squalls (SQ)
Ahead of convective clouds and CB Outflow of cold air Down-draughts Gust fronts
60
Line Squalls (LSQ)
A band of intense thunderstorms
61
Gust (G)
A sudden increase in wind speed of more than 10kts and lasting for only a few seconds
62
Seabreeze
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
Land Breeze
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
Thermals
Temperature versus dew point split could indicate possible thermals Cause the undershoot/overshoot affect
65
Pilot Actions Whilst Flying Through Thermals
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
Dust Devils
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
Dust Storms
Moderate to strong winds Instability <1000m visibility
68
Katabatic Wind
Night or in the early morning Land loses heat by terrestrial radiation Gravity pulls the cooler air down the slope
69
Anabatic Wind
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
Mountain Wave Requirements
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
Windward
Upwind side of the mountain
72
Leeward
Downwind side of the mountain
73
Mountain Wave Turbulence
Significant turbulence in the lee side | Down draughts and rotor zones below the crest
74
The Föehn Effect
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
The Föehn Wind
The föehn effect causes a warm, dry wind on the lee side of the mountain
76
Requirements for a Low Level Jet
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
The Low Level Jet
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
Characteristics of a Low Level Jet
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
Altocumulus lenticularis
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
Kelvin-Helmholtz Wave Cloud
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
Dangers of Mountain Waves
Updraughts (hypoxia/altitude bust) Downdraughts (exceed a/c climb capability) Rotor zones (exceed aileron roll rate)
82
Abnormal Throttle Position
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
Pilot Actions When Facing Mountain Waves
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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