visibility Flashcards

1
Q

what are the two major reasons for poor visibility?

A

air-based - mist fog or precipitation

ground-based - sea spray, dust, industrial pollution

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2
Q

what is the difference between fog and mist?

A

when water droplets are very small, mist occurs. if droplets are bigger and more concentrated, fog forms.

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3
Q

how do you determine the difference between fog and mist?

A

Mist is used if visibility is a least 1km and fog is used if its less ( can reduce to 20m).

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4
Q

what can fog do to light?

A

it can prevent light from going through and it can reflect the light back onto visible objects.

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5
Q

what can blowing snow do to visibility?

A

visibility may fall below 50m if the snow is thick and the lack of contrast can lead to disorientation.

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6
Q

what can granular snow do to visibility?

A

very cold temperature with bright sunshine will fall as granular snow, which reflects the sunshine and appear as tiny diamonds.

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7
Q

what can drizzle do to visibility?

A

visibility can be poor in drizzle and sometimes will be difficult to distinguish from fog.

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8
Q

how far can continuous heavy drizzle reduce visibility to?

A

400-500m

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9
Q

what can rain do to visibilty?

A

visibility in light to moderate rainfall is generally not bad up to 1km. heavy rain in temperature regions of the world can reduce visibility to 300m, torrential rain visibility can be up to 50m.

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10
Q

what can hail do to visibility?

A

produce severe visibility problems, short-lived, however.

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11
Q

what can smoke do to visibility?

A

rarely reduces visibility to 1000m, most problems are due to dry matter.

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12
Q

what can haze do to visibility?

A

minute dry particles in the air, together with low humidity, gives the air a smoky appearance, reducing visibility to a severe degree.

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13
Q

what can dust storms do to visibility?

A

hot desert regions, dust devils and whirlwinds may occur. Water particles accumulate around nuclei of dust particles. smog can appear if process is accelerated both reducing visibility

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14
Q

what can salt/sea spray do to visibility?

A

gale-force winds at sea may lift it into the atmosphere.

Salt particles attract moisture in the air and become effecting at reducing visibility.

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15
Q

what can volcanic eruptions do to visibility?

A

serious visibility problems occur after volcanic activity. force of eruption lifts debris high into the atmosphere where they may remain

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16
Q

how do you define prevailing visibility?

A

referring to surface conditions and means the shortest and greatest horizontal distance, including the directions at which objects can be recognised during the day.

17
Q

what is runway visual range (RVR)?

A

the visibility along the runway which may be different from the meteorological visibility.

18
Q

what does prevailing visibility report?

A

the distance at which objects can be recognised during the day.

19
Q

how is visibility at night assessed?

A

it’s assessed using the same methods as daytime visibility.

20
Q

at night with no objects visible what are pilots mainly concerned about?

A

the number of lights visible

21
Q

why does the sun or moon have no effect on prevailing visibility?

A

the distance at which you see objects during the night or day is dependent on factors such as the amount of water droplets and impurities in the air, the colour, brightness and size of the objects being focused on, or the sensitivity of your vision.

22
Q

what is the maximum distance that prevailing visibility will be reported?

A

9999m

23
Q

what happens to visibility as you climb to cloud layer?

A

visibility will usually deteriorate quite suddenly as the cloud base is reached?

24
Q

how is the distance at which objects can be recognized determined?

A

varies with direction in which the way you’re looking. objects towards the sun are less clear then objects away from it.

25
Q

if smoke or dust has accumulated near the ground where is visibility best?

A

above it, higher up.

26
Q

what is slant visibility range?

A

The farthest distance the pilot can see forward on the Earth’s surface.

27
Q

what is one of the characteristics of slant visibility range?

A

if there is a layer of fog over the aerodrome, there might be a great difference between the visibility at the surface and visibility from, say, a few thousand feet

28
Q

in slant visibility what will happen when u descend down the fog layer? And why?

A

horizontal visibility will temporarily become poor. Vertical visibility may not change significantly.

This is because the line of sight downwards takes a shorter path through the fog layer.