Visibility Flashcards
What is a visibility?
Maximum distance for recognising black object on bright background
What determines atmospheric visibility?
Atmospheric visibility is determined by the number of particles suspended in the air.
- MAY SCATTER OR OBSCURE LIGHT
How many meters for Fog (FG)?
less than 1000 m
How many meters for mist (BR)?
1000 - 5000 m
How many meters for haze (HZ)?
less than 5000 m
How many meters for smoke (FU)?
less than 1000 m
How many meters for volcanic Ash (VA)?
No specific number
What is difference between haze and volcanic ash?
Haze has particles of water while volcanic ash has solid particles
How many meters for Widespread Dust (DU)?
less than 5000 m
What is fog comprised of?
It is comprised of water droplets or ice crystals
How many meters for Widespread Sand (SA)?
less than 5000 m
What is radiation fog?
Fog that is confined to low ground\
- typical on non-tropical regions and far away from coasts
- Usually in Autumn
What are the three ingredients to make a fog?
High humidity, light wind and clear sky
How can fog clear away?
When does the fog form?
Usually at the winters, just after sunrise
What is advection fog?
It is when warm moist air from source regions colds down in colder region, which creates the fog
(it can be a stratus cloud)
Wat is steam fog?
When the air is colder than the water which creates steam fog
Where can steam fog typically be found?
By the lakes
What is a frontal fog?
The front of Nimbostratus cloud where the could rains
What is Hill/Upslope fog?
Mountain or hill fog, usually created by the föhne effect
How is radiation Fog formed?
Forms over the land on calm, clear nights in the autumn and winter months
How is Advection fog formed?
Created when warm moist air moves over a colder surface
How is steam Fog formed?
Created when cold dry air passes over a warm moist surface
Reduced visibility for Precipition?
It depends on rain, heavy rain and drizzle
