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MyMET > Visibility > Flashcards

Visibility Flashcards

1
Q

VFR minimum conditions?

A

Visibility greater than 5km
Vertical cloud distance 1000ft
Horizontal cloud distance 1.5km

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2
Q

4 non-atmospheric causes of low visibility

A
  1. Glare from the sun or a windscreen
  2. Contaminated windscreens
  3. Scratched windscreens
  4. UV damaged (acrylic) windscreens
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3
Q

5 atmospheric causes of low visibility

A
  1. Water droplets
  2. Ice crystals
  3. Smoke
  4. Chemical pollutants
  5. Volcanic ash
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4
Q

What visibility does fog imply?

A

Less than 1000m

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5
Q

What visibility does mist/haze/smoke/dust/sand imply?

A

1000m - 5000m

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6
Q

5 types of fog?

A
  1. Radiation fog
  2. Advection fog
  3. Evaporation/steam fog/artic smoke
  4. Frontal fog
  5. Hill/upslope fog
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7
Q

What are the ideal conditions for radiation fog?

A

High RH, light winds (2-8kt), clear skies
High pressure system over land
Nighttime temperature inversion

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8
Q

3 ways radiation fog disperses

A
  1. Temperature increases above dew point
  2. Wind mixing dry and saturated air
  3. May lift into a low St or Sc
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9
Q

What causes advection fog?

A

When a parcel of warm, moist air moves horizontally over a colder surface

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10
Q

What type of areas in advection fog associated with?

A

Cool sea areas adjacent to coasts in the summer

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11
Q

What causes Steam Fog/Arctic Fog/Sea Smoke?

A

Very cold air sitting over a warm, moist surface

As soon as water evaporates it condenses causing fog

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12
Q

What causes frontal fog?

A

Rain forces the cloud base down

Warm front over a cold front creates an inversion

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13
Q

What causes orographic/hill fog?

A

Air forced up a slope condenses and forms clouds, close to the surface these are fog

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14
Q

What is freezing fog?

A

Fog at a temperature below 0 degrees

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15
Q

What does freezing fog contain?

A

Supercooled water droplets which freeze on impact

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16
Q

What is fog below 2m depth?

A

Mist

17
Q

What is the weather abbreviation for patchy fog?

A

BCFG

18
Q

What is the weather abbreviation for partial fog?

A

PRFG

19
Q

What is the visibility in cirriform clouds?

A

1000m+

20
Q

What is the visibility in Ac and As?

A

20 - 1000m

21
Q

What is the visibility in Ns and Cb?

A

10 - 20m

22
Q

What is the visibility in Sc and St?

A

10 -30m

23
Q

What is the visibility in Cu?

A

Less than 20m

24
Q

What is smoke?

A

Suspension of small particles produced by combustion

25
Q

What is haze?

A

Suspension of extremely small, dry particles invisible to naked eye and sufficiently numerous to give the air opalescent appearance

26
Q

What is dust haze?

A

Suspension of dust or small sand particles, raise from the ground prior to the time of observation

27
Q

What wind speed do sand and dust storms require?

A

15kt+

28
Q

How high can sand and dust storms reach?

A

Dust storms - 15000ft

Sand storms - few hundred metres (heavier)

29
Q

Visibility in a heavy dust storm?

A

Less than 200m

30
Q

What happens to air-to-ground visibility when there is fog?

A

Reduces as you descend

31
Q

VFR operating minima on the ground?

A

Cloud ceiling greater than 450m/1500ft

Ground visibility greater than 5km

32
Q

How does a control tower report visibility observed?

A

Whatever it is for at least half of the horizon

33
Q

For visibility reporting what are the different increments?

A

0 - 800m = 50m increments
800m - 5km = 100m increments
5km - 10km = 1km increments
10km+ = 10km increments

34
Q

What does the USA use for reporting visibility?

A

Statute miles

35
Q

What is the runwa visual range (RVR)?

A

The range over which the pilot of an aircraft on the centreline of a runway can see the runway surface/edge lights/centreline lights

36
Q

Where are RVR detectors placed?

A

2.5m above the runway within 120m

Usually threshold, mid point and stop-end point

37
Q

When is RVR reported?

A

When RVR is below 1500m

38
Q

What do U, D and N indicate when reporting RVR?

A

U - upward visibility trend
D - downward visibility trend
N - neutral trend

39
Q

What is the ceiling also known as?

A

Vertical visibility (VV)

MyMET (22 decks)

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