Fog

Question 1

how is fog formed?

Answer 1

fog is formed by the different coolings of moist air below its dew point.

Question 2

how is fog classified?

Answer 2

it is classified according to its composition. e.g freezing fog apples when them moisture content is supercooled water.

Question 3

what are the conditions required for radiation fog?

Answer 3

clear night, moist air and light winds

Question 4

how is radiation fog formed?

Answer 4

on a clear night, the ground radiates heat rapidly. It receives no solar radiation in return, so the temperature falls near the ground. what happens next depends on wind strength.

The air nearest the ground is cooled by conduction. Dew point is reached at ground level and either dew or hoar frost forms, depending on temperature.

Question 5

what does the wind strength do during radiation fog?

Answer 5

light winds up to 5kts will spread the cooling effect virtually by turbulence.

If this cooling reaches dew point, fog forms. starts thin on the ground and extends upwards stronger winds allow for deeper vertical mixing in the surface layer even under radiative cooling.

Question 6

where does radiation fog never form?

Answer 6

never forms at sea because the water temperature doesn’t cool sufficiently, however radiation fog can drift out a short way to sea from land.

Question 7

where does radiation fog normally occur?

Answer 7

exclusively a land fog, valleys or low lying land are particularly subject to radiation fog, due to cooled air accumulating at base of hills.

Question 8

when does radiation fog normally occur?

Answer 8

Radiation fog forms during clear nights. This occurs most frequently with high-pressure systems. Radiation fog can occur in the autumn, spring and winter. The relatively feeble amount of solar heating received during the day is quickly lost by cooling during the evening.

Question 9

how is radiation fog dispersed?

Answer 9

Radiation fog is usually dispersed by solar radiation which warms the ground. The first effect could be a
thickening of the fog layer due to convection, which would rise and disperse.

Question 10

how does advection fog form?

Answer 10

advection fog forms when warm moist air moves over colder surfaces and is cooled below dew point.

Question 11

what happens to advection fog when further cooling below the dew point occurs?

Answer 11

results in denser and thicker fog.

Question 12

what is the relationship between windspeed and advection fog?

Answer 12

advection fog isn’t so dependent on the wind speed as radiation fog. up to about 15kts, the fog will become denser with increasing speed.

Question 13

what can advection fog do that radiation can’t?

Answer 13

unlike radiation fog, advection fog can also form in overcast conditions and over a lake or the sea.

Question 14

what happens to advection fog when winds go over 15kts?

Answer 14

winds above 15kts will cause fog to disperse and may be causing stratus cloud to form.

Question 15

what are the best conditions for advection fog to form?

Answer 15

moist air, surface temperature several degrees below the dew point of the air and moderate winds.

Question 16

How can advection fog disperse?

Answer 16

By a temperature change through advection, strong wings, or solar heating.

Question 17

When is advection fog most likely to form?

Answer 17

advection fog is most likely to form at sea, during spring and early summer, when the sea is comparatively cold. on land its more common in autumn season

Question 18

why is the relative temperature of the land and sea at different times of the year important to the formation of advection fog?

Answer 18

during spring and early summer, the land warms up due to solar heating, while the sea surface is still comparatively cold.

Question 19

how come advection fog formed at sea doesn’t disperse with solar heating?

Answer 19

it doesn’t disperse, since this doesn’t produce a significant change in sea surface temperature.

Question 20

where does advection fog normally form?

Answer 20

It’s most common along the coast, as sea breeze blows moist air over land.

Question 21

how is upslope fog formed?

Answer 21

Upslope fog or Hill fog is formed when stable air moves up over sloping terrain and is cooled
to the dew point. The name is also used for any cloud which is obscuring high ground

Question 22

what is the cooling process called?

Answer 22

Anabatic is a term used to describe air that moves up the slope of a valley when the land is warm.

When air moves over sloping terrain and cools, it is called Adiabatic cooling. Tcan occur equally on steep mountainsides and gently undulating terrain.

Question 23

what is frontal fog?

Answer 23

Fog forming during the passage of a front is known as Frontal fog

Question 24

how is frontal fog formed?

Answer 24

Rain is usually colder than the air through which it falls. But when it’s warmer.

Falling water droplets evaporate rapidly if their temperature is higher than the surrounding air, which add warm moisture to the cold air.

Mixing of the humid warm air from the evaporating droplets, with the surrounding colder air, leads to supersaturation, condensation, and finally fog.

Question 25

where does frontal fog usually occur?

Answer 25

typically occurs in cold air behind the warm fronts. Conditions such as this are normally found with weather fronts, where warm air is being lifted over cold air along a sloping surface.

Question 26

how is steam fog formed? And what’s the process?

Answer 26

when stable cold air moves over a warm water surface.

The air is warmed from below and intense evaporation takes place. Close to the surface of the water, warm humid air mixes with dry cold air, resulting in condensation by mixing.

Question 27

where does steam fog normally form?

Answer 27

polar regions, can also occur on inland lakes or rivers in cold weather, where it tends to resemble rising steam - hence its name.

Question 28

at what heights are steam fogs common?

Answer 28

Steam fog is generally quite shallow - between 50 and 200 feet. However, in those regions, which are affected by Arctic air, fog can build up to as high as 5000 feet

Question 29

Steam fog may also drift in over the land from the sea. What is likely to happen in this case?

Answer 29

If Steam fog drifts in over the land from the sea, the fog will become denser as the air is cooled over the coolest ground.