visibility

Question 1

what are the two major reasons for poor visibility?

Answer 1

air-based - mist fog or precipitation

ground-based - sea spray, dust, industrial pollution

Question 2

what is the difference between fog and mist?

Answer 2

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

Question 3

how do you determine the difference between fog and mist?

Answer 3

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

Question 4

what can fog do to light?

Answer 4

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

Question 5

what can blowing snow do to visibility?

Answer 5

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

Question 6

what can granular snow do to visibility?

Answer 6

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

Question 7

what can drizzle do to visibility?

Answer 7

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

Question 8

how far can continuous heavy drizzle reduce visibility to?

Answer 8

400-500m

Question 9

what can rain do to visibilty?

Answer 9

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.

Question 10

what can hail do to visibility?

Answer 10

produce severe visibility problems, short-lived, however.

Question 11

what can smoke do to visibility?

Answer 11

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

Question 12

what can haze do to visibility?

Answer 12

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

Question 13

what can dust storms do to visibility?

Answer 13

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

Question 14

what can salt/sea spray do to visibility?

Answer 14

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

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

Question 15

what can volcanic eruptions do to visibility?

Answer 15

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

Question 16

how do you define prevailing visibility?

Answer 16

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

Question 17

what is runway visual range (RVR)?

Answer 17

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

Question 18

what does prevailing visibility report?

Answer 18

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

Question 19

how is visibility at night assessed?

Answer 19

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

Question 20

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

Answer 20

the number of lights visible

Question 21

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

Answer 21

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.

Question 22

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

Answer 22

9999m

Question 23

what happens to visibility as you climb to cloud layer?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

above it, higher up.

Question 26

what is slant visibility range?

Answer 26

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

Question 27

what is one of the characteristics of slant visibility range?

Answer 27

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

Question 28

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

Answer 28

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.