Fog

Question 1

Fog is

a) A visible aggregate of minute water droplets that are based at the Earth’s surface and reduces horizontal visibility to less than 5/8 SM.

b) A visible aggregate of ice crystals that are based at approximately 200 feet above the surface and reduces horizontal visibility to less than 1⁄2 NM.

c) A visible aggregate of large water droplets that are based at the Earth’s surface and reduces horizontal visibility to less than 1 SM

Answer 1

A) A visible aggregate of minute water droplets that are based at the Earth’s surface and reduces horizontal visibility to less than 5/8 SM.

Question 2

When fog is composed of of ice crystals, it is termed

a) Freezing fog.

b) Ice fog.

c) Winter fog.

Answer 2

B) Ice fog.

Question 3

Fog composed of water droplets and occurring with temps at or below freezing is termed

a) Freezing fog.

b) Ice fog.

c) Winter fog.

Answer 3

A) Freezing fog.

Question 4

Fog forms when

a) The temperature and dewpoint of the air become identical (or nearly so).

b) The temperature and dewpoint of the air are within 10°C.

c) The temperature of the air is below 2°C.

Answer 4

A) The temperature and dewpoint of the air become identical (or nearly so).

Question 5

Types of fog are

a) Radiation fog.

b) Advection fog.

c) All are correct.

Answer 5

C) All are correct.

Question 6

Types of fog are

a) Frontal fog

b) Polar fog

c) All are correct.

Answer 6

A) Frontal fog

Question 7

Types of fog are

a) Upslope fog

b) Frontal fog

c) All are correct.

Answer 7

C) All are correct.

Question 8

Radiation fog is a common type of fog, produced

a) Over a land area when radiational cooling reduces the air temperature to or below its dewpoint.

b) When moist air moves over a colder surface, and the subsequent cooling of that air to below its dewpoint.

c) As a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain.

Answer 8

A) Over a land area when radiational cooling reduces the air temperature to or below its dewpoint.

Question 9

Radiation fog is generally

a) An evening occurrence and often does not dissipate until after sunset.

b) A nighttime occurrence and often does not dissipate until after sunrise.

c) A dawn occurrence and always dissipates before noon.

Answer 9

B) A nighttime occurrence and often does not dissipate until after sunrise.

Question 10

Some factors favoring the formation of radiation fog are

a) A shallow surface layer of relatively moist air beneath a dry layer.

b) Clear skies

c) All are correct.

Answer 10

C) All are correct.

Question 11

Advection fog forms

a) Over a land area when radiational cooling reduces the air temperature to or below its dewpoint.

b) When moist air moves over a colder surface, and the subsequent cooling of that air to below its dewpoint.

c) As a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain.

Answer 11

B) When moist air moves over a colder surface, and the subsequent cooling of that air to below its dewpoint

Question 12

Advection fog is common

a) Along coastal areas, but often moves deep in continental areas.

b) In river valleys late at night.

c) Along coastal areas only, dissipates quickly when wind moves it inland.

Answer 12

A) Along coastal areas, but often moves deep in continental areas.

Question 13

Advection fog can deepen as

a) Winds remain calm for a long period of time.

b) Wind speed increases up to about 15 kts.

c) Wind speed increases up to around 25 kts.

Answer 13

B) Wind speed increases up to about 15 kts.

Question 14

Advection fog can move rapidly

a) Regardless of the time of day or night.

b) During the morning hours immediately after sunrise.

c) Late in the afternoon before sunset.

Answer 14

A) Regardless of the time of day or night.

Question 15

Upslope fog forms

a) Over a land area when radiational cooling reduces the air temperature to or below its dewpoint.

b) When moist air moves over a colder surface, and the subsequent cooling of that air to below its dewpoint.

c) As a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain.

Answer 15

C) As a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain.

Question 16

When warm moist air is lifted over a front, clouds and precipitation may form. If the cold air below is near its dewpoint , evaporation (or sublimation) form the precipitation may saturate the cold air and

a) Radiation fog may form.

b) Frontal fog may form.

c) Advection fog may form.

Answer 16

B) Frontal fog may form.

Question 17

Frontal fog is most commonly associated with

a) Warm fronts, but can occur with other fronts as well.

b) Occluded fronts.

c) A frontal wave.

Answer 17

A) Warm fronts, but can occur with other fronts as well.

Question 18

Steam fog forms

a) When very cold air moves across relatively warm water, enough moisture may evaporate from the water surface to produce saturation.

b) When moist air moves over a colder surface, and the subsequent cooling of that air to below its dewpoint.

c) As a result of moist, stable air being adiabatically cooled to or below its dewpoint as it moves up sloping terrain.

Answer 18

A) When very cold air moves across relatively warm water, enough moisture may evaporate from the water surface to produce saturation.

Question 19

Advection fog has drifted over a coastal airport during the day. What may tend to dissipate or lift this fog into low stratus clouds?

a) Nighttime cooling.

b) Surface radiation.

c) Wind 15 knots or stronger.

Answer 19

C) Wind 15 knots or stronger.

Question 20

What lifts advection fog into low stratus clouds

a) Nighttime cooling.

b) Dryness of the underlying land mass.

c) Surface winds of approximately 15 knots or stronger.

Answer 20

C) Surface winds of approximately 15 knots or stronger.

Question 21

In what ways do advection fog, radiation fog and stem fog differ in their formation or locations

a) Radiation fog is restricted to land areas; advection fog is most common along coastal areas; steam fog forms over a water surface.

b) Advection fog deepens as windspeed increases up to 20 knots, steam fog requires calm or very light wind; radiation fog forms when the ground or water cools the air by radiation.

c) Steam fog forms over moist air moving over a colder surface; advection fog requires cold air over a warmer surface; radiation fog is produced by radiational cooling of the ground.

Answer 21

a) Radiation fog is restricted to land areas; advection fog is most common along coastal areas; steam fog forms over a water surface.

Question 22

With respect to advection fog, which statement is true

a) It is slow to develop, and dissipates quite rapidly.

b) It forms almost exclusively at night or near daybreak.

c) It can appear suddenly during day or night, and it is more persistent than radiation fog.

Answer 22

C) It can appear suddenly during day or night, and it is more persistent than radiation fog.

Question 23

In which situation is advection fog most likely to form

a) An air mass moving inland from the coast in winter.

b) A light breeze blowing colder air out to sea.

c) Warm, moist air settling over a warmer surface under no-wind conditions.

Answer 23

A) An air mass moving inland from the coast in winter.

Question 24

What type of fog depends upon a wind in order to exist

a) Steam for and down slope fog.

b) Precipitation-induced fog and ground fog.

c) Advection fog and up slope fog.

Answer 24

C) Advection fog and up slope fog.

Question 25

Which conditions are favorable for the formation of radiation fog

a) Moist air moving over colder ground or water.

b) Cloudy sky and a light wind moving saturated warm air over a cool surface.

c) Clear sky, little or no wind, small temperature/dew point spread, and over a land surface.

Answer 25

C) Clear sky, little or no wind, small temperature/dew point spread, and over a land surface.

Question 26

Low level turbulence can occur and icing can become hazardous in which type of fog

a) Rain-induced fog.

b) Upslope fog.

c) Steam fog.

Answer 26

C) Steam fog.

Question 27

What is the most prevalent warning that radiation fog will form

a) Little or no wind.

b) Moist air moving over cold ground.

c) All are correct.

Answer 27

C) All are correct.