Visibility(oxford)

Question 1

Explain radiation fog:

For radiation fog to form, the wind must be a -

What kind of phenomenon will result because of radiation fog?

If a strong wind is combined with radiation fog -

Locations of radiation fog:

Radiation fog is dispersed by -

Answer 1

Radiation fog is caused by radiation of the earth’s heat at night, and the conductive cooling of the air in contact with the ground to below dew point. If there is a light wind, then fog will form, and in calm conditions the result will be the formation of dew.

light wind(2 - 8kt)

Inversion above

stratus cloud could form

• Over land - not over sea because there is little DV of temperature.
• Firstly in valleys because of the katabatic effect.
• In anticyclones, ridges and cols.

the sun or strong wind(which will result in stratus)

Question 2

Explain hill fog(orographic fog):

Answer 2

Hill fog is usually stratiform cloud which base is below the summit of the hills. Caused when warm moist air is forced over high ground/

Question 3

Explain advection fog:

The wind must be -

Dispersal:

Answer 3

Caused when warm moist air move over a cold surface, the surface can be land or sea.

up to 15kt to move the air

Wind greater than 15kts which will lift to generate stratus cloud

Question 4

Frontal fog occurs -

The main cause -

the fog can form a -

Answer 4

at a warm front or occlusion

precipitation lowering the cloud base

belt of up to 200nm travelling with the front

Question 5

Explain The Bergeron theory:

However -

which will provide -

Freezing fog will also occur when the dew point is above _°C forming fog but the air then cools to a temperature less than _°C.

Answer 5

At temperatures below 0 degrees air become saturated for the formation ice before it becomes saturated for the formation of water. Hence water vapour will go directly to the solid state at these temperatures.

the rarity of freezing nucleii in the atmosphere means that when the dew point is below 0°C condensation will take place producing supercooled water droplets. These droplets will then freeze on contact with a solid object.

hoar frost (or rime ice).