Chapter 9

Question 1

Fog is generally considered as

Answer 1

an atmospheric hazard

Question 2

Fog is a form of

Answer 2

condensation such as dew, frost and clouds but it is formed above the ground at low levels.

Question 3

The essential deference between fog and cloud is

Answer 3

the method and place of formation.

Question 4

Clouds need an

Answer 4

upward motion to form

Question 5

. Clouds need an upward motion to form. The lifting process causes

Answer 5

the parcel of air to lift to a higher levels and cools adiabatically to condense.

Question 6

Fog results from

Answer 6

cooling or by the addition of enough water vapor to cause saturation.

Question 7

Fog results from cooling or by the addition of enough water vapor to cause saturation. Fog needs a

Answer 7

light to moderate wind to form

Question 8

Fog results from cooling or by the addition of enough water vapor to cause saturation. Fog needs a light to moderate wind to form. Strong wind

Answer 8

disperses the air before it reaches saturation

Question 9

1- Fog formed by cooling:

Answer 9

1. Radiation fog
2. Advection fog
3. Upslope fog

Question 10

Fog formed by cooling: (how it forms)

Answer 10

When temperature of a layer of air in contact with the ground falls below its dew point condensation produces fog

Question 11

Radiation fog (conditions)

Answer 11

radiation cooling of the ground and adjacent air.

In clear nights and fairy high relative humidity the continuous cooling may produce fog in early morning.

A necessary condition to form a fog is a light wind. A light wind of 3-4km/h creates enough turbulence to carry the fog upward 10 to 30 meters above the ground without dispersing it

Question 12

Advection fog (conditions)

Answer 12

When warm and moist air is blown over a cold surface, it becomes chilled by contact and to a certain extent, by mixing with the cold air created by cold surface below. If cooling is sufficient the result is advection fog.

Advection fog needs a wind of 10-30 km/h, because that advection fog is often thick may have a thickness of 300-600 m.

Radiation fog may form at anytime of a day and persist for many hours.

Question 13

Upslope fog:

Answer 13

Upslope fog is created when relatively humid air moves up a gradual sloping plain or in some cases, up the steep slopes of a mountain because of the upward movement, air expands and cools adiabatically. In a stable air if the dew point is reached an extensive layer of fog may form.

Question 14

Fog formed by evaporation:

Answer 14

• Steam fog
• Frontal fog

Question 15

Fog formed by evaporation (how it forms)

Answer 15

Fog may form when saturation occurs primarily because of the addition of water vapor. The resulting fog is called evaporation fog

Question 16

Steam fog

Answer 16

When cool air moves over warm water enough moisture may evaporate from the water surface to saturate the air immediately above

Question 17

Frontal fog:

Answer 17

When precipitations fall passing through the frontal slope, part of these precipitations evaporates in cold air below the frontal slope. If the cold air near saturation, the evaporation may reach saturation and fog may form. This type of fog is called frontal or precipitation fog.

Question 18

Frost and dew:

These phenomena are forms of

Answer 18

condensation at the ground

Question 19

Frost and dew:

These phenomena are forms of condensation at the ground. They are generally results from

Answer 19

radiation cooling on clear, cold nights

Question 20

Dew is

Answer 20

the condensation of water vapor on objects that have radiated sufficient heat to lower their temperature below the dew point of the surrounding air.

Question 21

Because different objects radiate heat at different rates dew may

Answer 21

form on some surfaces but not on others.

Question 22

Dew is more frequent on

Answer 22

grass because the transpiration of water vapor by the blades rises the relative humidity to higher levels directly above the grass.

Question 23

Dew is an important source of

Answer 23

of moisture in dry regions. During summer time it is very necessary.

Question 24

The conditions of dew formation are:

Answer 24

1. clear, cold nights; 2. calm wind

Question 25

Frost has similar conditions of formation as

Answer 25

dew except that it forms when the temperature falls below freezing point

Question 26

Frost has similar conditions of formation as dew except that it forms when the temperature falls below freezing point, thus frost forms when

Answer 26

water vapor changes directly from gas into solid without entering the liquid state. This process of changing state is called deposition

Question 27

Frost has similar conditions of formation as dew except that it forms when the temperature falls below freezing point, thus frost forms when water vapor changes directly from gas into solid without entering the liquid state. This process of changing state is called deposition. It produces

Answer 27

delicate patterns of ice crystals that frequently decorate windows in winter

Question 28

Types of frost:

Answer 28

1. Radiation frost
2. Advection frost

Question 29

Radiation frost forms under these conditions:

Answer 29

1. sufficient cooling at clear nights;
2. the temperature falls below 0^oC; and
3. calm to light wind.

Question 30

Radiation frost forms in

Answer 30

valleys early morning, when the air is stable (in clear, cold nights).

Question 31

Advection frost:

Answer 31

It forms when a cold air mass moves toward a dry surface. It forms anytime on mountain slope. A mixing of the two types of frost may occur.