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CPL Met > Met Lesson 3 > Flashcards

Met Lesson 3 Flashcards

1
Q

Air Mass Source Region Types

A

Sea/land: maritime/continental

By latitude: tropical/polar

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2
Q

4 Air Mass Source Regions

A 
Tropical maritime (Tm)
Tropical continental (Tc)
Polar maritime (Pm)
Polar continental (Pc)
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3
Q

Source Regions Affecting the Characteristics of Air Masses

A

Air takes on the characteristics of the surface its over
Continental air masses lose moisture due to contact with the land
Air within Polar cell = polar air
All other air cells are comprised of tropical air

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4
Q

A Front

A

The boundary between two different temperature air masses

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5
Q

Cold Fronts

A

Warm air forced to rise over heavier cold air
Cold, dense air will wedge in under the warmer air
Very little mixing due to the different densities

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6
Q

Weather in an Approaching Cold Front

A 
Reducing pressure (rising air particles)
Northwest winds
Cumulus clouds and showers
Cb if the warm air is conditionally unstable
Altocumulus and altostratus cloud
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7
Q

Ahead of the Cold Front

A

Gusts and squalls
Fast moving low cloud
Turbulence
Possible squall line

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8
Q

Passing Cold Front

A

Increasing pressure
Northwest wind backing to Southwest winds
Reducing temperature
Cumulus/towering cumulus/small cumulonimbus as frontal inversion increases with height

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9
Q

Warm Front

A

Warm less dense air will gradually slope up against the colder and more dense air

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10
Q

Weather Associated with a Warm Front

A

If the warm air is stable: Cirrus and cirrostratus creating the halo effect
Cloud becomes thicker and lower with passing front
Altocumulus, altostratus, nimbostratus
Heavy and continuous rain
If the warm air is less stable more cumulus will develop

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11
Q

Weather Associated with a Passing Warm Front

A

Warm air advancing over a cold ground creates a stable environment and the cloud will clear rapidly
Fair weather

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12
Q

Wave Depressions

A

A low pressure system is formed on the tip of the cold front as the warm air is being lifted by the cold air
The cold air swings (veers) around and catches up with the warm front because the colder air is heavier
Once it catches up it produces an occluded front

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13
Q

Occluded Front

A

Fast moving cold front catches up with the slower moving warmer air
The cold air forces the warm front upwards

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14
Q

Embedded Cumulonimbus

A

Thunderstorm obscured by other types of cloud

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15
Q

Stationary Front

A

When two air mass systems become stationary and there is no resultant movement present
When some upper air disturbance occurs the stationary system becomes displaced

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16
Q

Visibility

A

The greatest horizontal distance at which a person can identify a dark object with normal eyesight
May be specified for each direction and reported in m or km

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17
Q

Visibility Obscurations

A 
Reduce in-flight visibility
Moisture - precipitation/fog/cloud/etc
Smoke
Pollution
Dust/sand
Sun - glare, light/darkness
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18
Q

Reported Visibility

A

Visibility from the ground reported by an accredited observer on the ground

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19
Q

Flight Visibility

A

Horizontal visibility as observed by the pilot from the cockpit when in flight

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20
Q

Slant Visibility

A

The air to ground visibility observed by the pilot from the cockpit when in flight

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21
Q

Night and Day Visibility

A

Night visibility is normally better than daylight visibility

Daylight visibility is the worst at dawn and dusk

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22
Q

Vertical Visibility

A

Air to ground visibility when above the object (ft)

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23
Q

Runway Visual Range

A

Maximum distance that the runway can be seen from the average eye level of the pilot at touchdown
Measured with electronic instruments installed next to an ILS equipped runway

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24
Q

Dew

A

Water vapour condensates onto objects in the form of dew when sufficient moisture is available during overnight cooling
Normally after a clear night with sufficient moisture

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25
Q

Frost

A

The temperature of the ground is below 0°C
Frozen dew
Disrupts laminar airflow over the wing, loss in lift and increase in drag
Cooling effects on the wing due to acceleration

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26
Q

Conditions Required for Icing

A

Visible moisture, near freezing temperatures, super cooled water droplets (subzero water in liquid state)
Freezing temperatures
Freezing airframe temperature
Resistance to freezing due to spherical shape
Any disturbance/shock to change the shape of the droplet, allows the release of latent heat and freezing

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27
Q

Hoar Frost

A

Nighttime cooling close to the ground
Deposits of ice crystals
Doesn’t require super cooled water droplets for formation

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28
Q

Affects of Hoar Frost on Aircraft

A

Negatively affects the aerodynamics of the wings
May occur when aircraft cruising in cold altitudes
Airframe cools down - cold soaking
On descent, the aircraft enters warmer air and turns to frost via deposition

29
Q

Rime or Clear Ice

A

Usually both present, however one type tends to predominate
Type depends upon the supercooled water droplet size and the type of cloud
Larger droplets require a larger cloud as strong up draughts are required

30
Q

Catch Efficiency

A

A thicker wing will catch more water

Thicker is better

31
Q

Clear Ice

A

0°C to -15°C
Large drops of freezing rain
The drop flows backwards on the surface and spreads before it freezes as it loses more latent heat in warmer conditions
No air is trapped inside the ice making it transparent and difficult to see

32
Q

Clouds Producing Clear Ice

A

Cumuliform
Nimbostratus cloud
Thick altostratus

33
Q

Rime Ice

A

-10°C to -20°C
Small supercooled water droplets
Opaque in colour due to air pockets within the droplets

34
Q

Clouds Producing Rime Ice

A

Altostratus
Altocumulus
Cumulus tops
Stratiform above the freezing level

35
Q

Surface Areas Mostly Affected by Icing

A 
Wing leading edges
Windscreens
Tail section
Engine/propellers/engine intakes
Antennae
36
Q

Affects of Icing on an Aircraft

A 
Increase in drag
Increase in weight
Decrease in lift
Decrease in thrust
Blocked pitot tubes
Decreased visibility
May restrict control surfaces
Reduced breaking action on the runway
37
Q

Icing Due to Warm Fronts

A

Rain falling from the warmer air through the colder air may become severe clear ice
Flying into a lowering cloud base due to a warm front may lure you into severe icing conditions

38
Q

Differences from Fog and Cloud

A 
Height at which they occur
Formation process (fog from conduction)
39
Q

Fog and Mist

A

Natural visibility reducing phenomenas just above the ground level

40
Q

Fog

A

Horizontal visibility < 1000m

41
Q

Mist

A

Horizontal visibility => 1000m

42
Q

Conditions Required for Radiation Fog

A

Light winds < 5kts
Clear skies at night (max terrestrial radiation)
High relative humidity (more humid = more likely for dew point to be reached)

43
Q

The Clearing of Radiation Fog

A

Winds > 5kts
An increase in solar heating
A decrease in humidity

44
Q

The Effects of Solar Heating on Radiation Fog

A

Initially after sunrise the fog thickens due to the increased mixing by solar heating (also the coldest time of the day)
Thin and evaporates from below as the ground surface heats up

45
Q

Advection Fog

A

Warm humid air passing horizontally over a cold surface
May form at any time of day or night
May persist for days
Eg. Warm humid air from tropical oceans over polar surfaces

46
Q

Dissipation of Advection Fog

A

Wind > 15kts
Reduced humidity due to deposition of water droplets on vegetation
Change in wind direction

47
Q

Fog Due to Mixing

A

Radiation for = 2 - 5kts (light wind)
Small or no difference between OAT and dew point
Advection fog = 10 - 15kts (stronger wind

48
Q

Frontal Fog

A

Cloud forms on the frontal boundary of the warm front

Warm rain causes the colder air below to become saturated

49
Q

Steam Fog

A

Cold moist air flows over warmer water

Evaporation from the water surface causes the air to become saturated

50
Q

Dangers of Fog and Haze

A

Slant visibility obscurations

Poor visibility

51
Q

Requirements for the Formation of Thunderstorms

A
  1. An unstable atmosphere (ELR > 3°C/1000ft) or conditionally unstable
  2. An abundance of moisture
  3. Lifting mechanism (convection, orographic lifting, frontal, convergence)
52
Q

Stages of a Thunderstorm

A
  1. Cumulus/growing/developing stage
  2. Mature stage
  3. Dissipating stage
53
Q

Cumulus Stage

A

Strong up draughts

No precipitation

54
Q

Mature Stage

A 
First gust
Lightning
Wind change 180° = runway change
Strong up and down draughts
20 - 30 mins
Rain showers begin
55
Q

Dissipating Stage

A

Continuous precipitation until the cloud is empty (rains out)
Storm moves away in the direction of the anvil

56
Q

Thunderstorm Hazards

A 
Lightning strike (compass swing)
Static electricity
Gust/dust storms
Turbulence and windshear
Temporary affects on night vision due to lightning flashes
Poor visibility
Severe airframe icing
Aquaplaning
Hail
Excessive cockpit noise
57
Q

Down Draughts Due to Cloud

A

Strong underneath the clouds
Virga
Down draughts due to an air mass becoming heavier and more dense than the warmer air

58
Q

Microbursts

A

Often associated with cumulonimbus clouds
Very strong downburst with a diameter of 4km
Avoid cumulonimbus by 20nm
Airflow spreads out near the ground
Severe windshear

59
Q

Tropical Cyclones

A

Small intense low pressure systems over warm ocean

Generally occur in the Southern hemisphere summer: November to April

60
Q

Formation Requirements for Tropical Cyclones

A

Narrow band of latitude in the Southern Hemisphere (5° - 15° South)
In this area the oceans are warm and the coriolis force is strong enough for rotation
When the cyclone is too close to the equator it has less of a spin as the coriolis force is weaker

61
Q

The 4 Stages of A Tropical Cylone

A
  1. Formative
  2. Immature
  3. Mature
  4. Decaying
62
Q

Formative Stage of a Tropical Cyclone

A

Eye forming
Humid air pulled into the low and forced to rise via convergence
Air cools adiabatically: dew point reached and cloud forms
Condensation releases latent heat, causing faster rising due to an increase in temperature
< 1000hPa

63
Q

Immature Stage of a Tropical cyclone

A

Strong winds
Pressure gradient steepens as pressure beneath becomes lower
Sucks more air in and the cycle continues
Winds light and variable inside the eye
Strong winds > 120kts around the eye with CB’s

64
Q

Mature Stage of a Tropical Thunderstorm

A

Surface pressure about 950hPa remaining constant
Strongest wind in the left forward quadrant due to steepest pressure gradient
Nimbostratus with spiral bands of cumulus and cumulonimbus, cirrus on top
Heavy rain clouds around the eye
Cloud-free eye as the temp is above dew point due to the release of latent heat

65
Q

Decaying Stage of a Tropical Thunderstorm

A

Rain depression
Die-out or become rain depressions once they move inland or move towards the colder pole (water temp < 26°C) or beyond 15°S
Due to reduced up draughts and water vapour supply
Colder and drier air over the ground (increased surface friction)
Widespread rain may continue for several days

66
Q

Tornados in North America

A

Great plains are exposed to cold and warm air
Massive convergence with sharply inclined isobars
Rotating twist due to differing winds that becomes a spiral

67
Q

Tornado

A

Massive super cell thunderstorm
<300m in diameter
Wind speeds up to 200kts
Central pressure rotating funnel 50hPa lower than the surrounding air: buildings explode as the tornado passes over

68
Q

Funnel Cloud

A

Doesn’t touch the ground

69
Q

Waterspouts

A

Touching the water surface and sucking water up

CPL Met (4 decks)

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