Chapter 16 - Visibility Flashcards
What is the visibility for Fog
less than 1000m
What is the visibility for Mist
1000m or more
What is the visibility for Haze
0 - 5000m
Radiation Fog has 3 requirements and expected to develop at
All the heat radiates away over night because of clear skies.
Humidity High
2-8 knots of light winds
ground to 500ft
often isothermal fog layer
Valley Fog is created
Is when the cold air katabtically drops into moist valley.
Orographic Fog
Is cloud develop on top of hills but in contact with the surface
Frontal Fog
Ahead of a warm front - after rain and surface is wet causing lots of evaporation
Ice Fog
High latitude, dry air, ice crystals
Ice Fog
High latitude, dry air, ice crystals
Haze is from
Solid Particles
Smog is from
Smoke and Fog
Main visibility is measured how
Look out at objects with certain distances in a 360 degree process. has to be over 50% all round to give figure
Secondary Visibility is
Less than 50% distance
If up to 800m its reported in
50m steps
If up to 800-5000m its reported in
100m steps
If up to 10km its reported in
1 km steps
9999 =
10km or more
Runway Visual Range =
Surface visibility in direction of landing
How and where is RVR measured
By a transmissometer (7 and a half feet up), situated at threshold (300m) , mid point (1000-1500m) and stop end.(300m) - done every 60 seconds
How often are updates of RVR for ATC and METARS
ATC - averaged over 1 min
METAR - average over 10 mins
If the Visibility has a U,D and N next to it what does it mean
Increasing Visibility = U
Decreasing Visibility = D
No change = N
Vertical Visibility - is measured 100’s feet how is it presented for 200 feet
VV002
To what is the difference between fog and mist compared to haze
humidity has to be high for fog and mist
