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Question 1

Define Fog

Answer 1

A suspension of either water droplets, ice crystals or both at the surface of the earth.

Question 2

What condition must be occurring, and what are the 2 ways condensation can occur for fog to form

Answer 2

An inversion must be present
the air must be cooled to it’s dew point
water vapour must be added to the air to bring the dewpoint up to the temperature

Question 3

3 factors that control the evolution of fog

Answer 3

Cooling of the air
addition of water vapour
mixing

Question 4

What are the types of fog caused by cooling of the air

Answer 4

upslope fog is formed as a result of adiabatic cooling
radiation fog is formed as a result of radiation cooling
advection fog is formed as a result of advection cooling

Question 5

what are the types of fog caused by adding water vapour to the air

Answer 5

Frontal fog (warm rain fog)
Steam fog, arctic steam fog
ice fog

Question 6

radiation fog

Answer 6

-earth continues to re-radiate suns energy after sun sets, cooling the earth
-cool earth cools warmer air above it
-temperature decreases to dewpoint, saturation occurs
-relatively warm air over cold land surface
-forms on land on clear days, usually in the morning
requires
-clear night
-light winds (3-5kts)
-high RH
-condensation nuclei

Question 7

Advection fog

Answer 7

• Moist warm air moves over a relatively cold surface
• moderate wind speed (13-17 kts)
• high RH
• Condensation nuclei
• can form on land or water
• will not dissipate over water during the day
• if wind speeds are higher, clouds will form at the top of the turbulent layer, lower wind will mean a thinner layer of fog

Question 8

Upslope fog

Answer 8

• air is lifted adiabatically and cools by expansion to dew point
• moderate wind speed (higher speed will cause cloud)
• high RH
• condensation nuclei

Question 9

Pre-frontal fog

Answer 9

-warm rain falls through cold nearly saturated air
-evaporation takes place, supersaturation occurs, extra water vapour condenses.
-forms ahead of a warm front and in cold air after cold frontal passage
-warm air over cold air
-warm frontal precipitation
-high RH
-Condensation nuclei
-

Question 10

Steam fog

Answer 10

• water vapour is released from warm water to cooler air above
• condensation occurs when dewpoint is raised to temperature
• shallow unstable layer of air above water surface
• happens in arctic when air moves from an ice covered surface to warmer water.

Question 11

Ice Fog

Answer 11

• Man made
• very cold temps
• strong surface inversion
• formed from ice crystals caused by the addition of water vapour through fuel combustion
• will build up if winds are light
• -30c

Question 12

2 factors that control the dissipation of fog

Answer 12

• heating of the air

- decrease in water vapour

Question 13

4 ways of heating the air

fog dissipation

Answer 13

• solar radiation
• advection over a warm surface
• adiabatic heating
• turbulent mixing

Question 14

2 ways of decreasing water vapour

fog dissipation

Answer 14

• turbulent mixing of fog with drier air above

- condensation of water vapour in the form of dew or hoar frost