Visibility Reporting Flashcards
When it comes to air based impediments of visibility - what are the main causes?
- Snow
- Sleet
- Drizzle
- Rain
- Hail
What are the two types of things that inhibit visibiltiy
Air based
Ground Based
What causes Haze?
Low humidity
Small particles in the air
( usually summer effect )
What ground based things impair visibitily?
What are the 3 types of visibility measurement?
Prevailing / Meteorological Vis - METARS / TAFs
RVR - Runway visibility
Flight Visibility - what we can see in flight
Is night visibility measured differently from day?
NO. Assuming the same atmospheric condtions, the same measurement will be there.
However, as pilots we care about the ability to see lights.
How is the RVR ( runway visibility range ) measured?
Either:
- Observer
- Transmissometer ( usually 3 down the runway, threshold, mid, end ) - uses a light source and measureing tool
Note: the mechnical device does not take into account human factors, such as contrast etc.
What is the slant range?
Maximum limit on visibility due to earth’s curvature.
Using visibility how is Fog defined vs Mist?
Fog < 1km
Mist > 1km
What is slant visibility? and how can fog/mist affect it?
The range a pilot can see from the cockpit.
In fog/mist - forward is reduced, vertical may stay high ( depends on the thickness of the layer )
What are the types of Fog?
Radiation Fog
Advection Fog
Upslope Fog
Frontal Fog
Steam Fog
What are the classifications of Fog?
Freezing
Warm
Ice
Shallow
What is radition fog - why does it form.
Formed due to cooling of the earth. Needs:
Moist Air
Clear Night
Light winds ( no more than 5 kts )
Usually forms under high pressure systems
Cause
Earth cools and lowers temp to dew point
Occurs Autumn, Spring Winter
Usually under high pressure systems
Locations
Low lying areas ( cold air moves into valleys )
Does not form at sea ( surface is too warm )
What is Advection Fog?
Warm moist air moves over a cold surface.
Wind upto 15kts
The surface temp is serveral degrees below Dew Point.
Can form over lakes/sea
Time of year
Land - autumn, winter
Sea - Spring and Winter
What is upslope fog?
Cold air force upwards by land mass
Light to moderate winds
Too much wind results in clouds ( stratus or cumulus )
What is frontal fog?
With a front, rain falls through dry air and evoporates - latent heat causes a warm part. This mixes with the cold surrounding air.
Fog happens where the front is close to the ground.
What is steam fog?
stable cold air mass moves over water surface.
Inland lakes and rivers ( polar regions too )
Usually thin ( 50 - 200 ft )
