visibility Flashcards
what are the two major reasons for poor visibility?
air-based - mist fog or precipitation
ground-based - sea spray, dust, industrial pollution
what is the difference between fog and mist?
when water droplets are very small, mist occurs. if droplets are bigger and more concentrated, fog forms.
how do you determine the difference between fog and mist?
Mist is used if visibility is a least 1km and fog is used if its less ( can reduce to 20m).
what can fog do to light?
it can prevent light from going through and it can reflect the light back onto visible objects.
what can blowing snow do to visibility?
visibility may fall below 50m if the snow is thick and the lack of contrast can lead to disorientation.
what can granular snow do to visibility?
very cold temperature with bright sunshine will fall as granular snow, which reflects the sunshine and appear as tiny diamonds.
what can drizzle do to visibility?
visibility can be poor in drizzle and sometimes will be difficult to distinguish from fog.
how far can continuous heavy drizzle reduce visibility to?
400-500m
what can rain do to visibilty?
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.
what can hail do to visibility?
produce severe visibility problems, short-lived, however.
what can smoke do to visibility?
rarely reduces visibility to 1000m, most problems are due to dry matter.
what can haze do to visibility?
minute dry particles in the air, together with low humidity, gives the air a smoky appearance, reducing visibility to a severe degree.
what can dust storms do to visibility?
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
what can salt/sea spray do to visibility?
gale-force winds at sea may lift it into the atmosphere.
Salt particles attract moisture in the air and become effecting at reducing visibility.
what can volcanic eruptions do to visibility?
serious visibility problems occur after volcanic activity. force of eruption lifts debris high into the atmosphere where they may remain