Anticyclones And Depressions

Question 1

Associated weather in winter for anticyclones

Answer 1

• cold daytime temp from 0-5 degrees
• very cold nighttime temperature
• clear skies by day and night, may have radiation fog (rapid loss of heat at night) in areas
• high levels of atmospheric pollution caused by subsidising air and lack of wind, tapped by temp inversion.

Question 2

Anticyclones and their associated weather in summer

Answer 2

• hot daytime temp - above 25c
• warm night time temp - not below 15c
• generally clear skies day and night
• thunderstorms from when air has high relative humidity.

Question 3

What are anticyclones called that establish over Britain and remain stationary for many days?

Answer 3

Blocking anticyclones.

Question 4

What does blocking anticyclones result in for winter and summer?

Answer 4

Winter - freezing and dry

Summer - heatwaves

Question 5

What type of fog is associated with anticyclonic conditions

Answer 5

Radiation fog

Question 6

What type of weather do you need for radiational fog to form?

Answer 6

Clear skies and moist air.

Question 7

How does radiational fog form?

Answer 7

• moist atmosphere above ground is cooler as a result of heat leaving ground through radiation.
• cooling extends some distance into the air, encouraged by light winds mixing the cool air.
• air cooled to dew point where it condenses turns into rain drops.
• warm air having not been cooked by ground forms temperature inversion
• disperses through winds of through warm air so evaporates.

Question 8

Why is radiational fog common in winter?

Answer 8

• long hours of darkness allows maximum radiational cooling.

Question 9

Fog formation under a temperature inversion in a valley?

Answer 9

• occur often in valleys.
• in evening clear skies and high humidity.
• air on upper slopes chill more quickly than that in Valley bottom.
• cooling increases density of air and begins to move downwards.
• cooling air displaces warmer air at valley bottom pushing warmer air upwards.
Cold air in bottom form few point and create a dense fog and severe frost

Question 10

What are advection fogs sometimes called?

Answer 10

Haar or fret.

Question 11

Where does advection fog usually occur?

Answer 11

Most common around coasts and over sea in summer (when sea is colder than land.)

Question 12

How does advection fog form?

Answer 12

• forms when a mass of relatively warm air moves horizontally over a cool surface.
• usually when moist warm air in contact with cold sea, hence cooling it, making it reach dew point and condense forming fog.
• common along coasts and over sea in summer.
• as Fog moves inland warmed by inland air and is dispersed.

Question 13

Formation of cold or thermal anticyclones

Answer 13

• occur over land masses in winter and polar areas most of the year.
• interiors of continental areas, land cools rapidly in winter
• heat loss by radiation.
• air in contact with ground is cooled, and sinks
• colder the ground, greater depth of atmosphere affected
• upto 2-3 km.
• cold air is dense and sinks, forming high pressure.
• over land masses in northern hemisphere and are easily displaced by depressions.
• British Isles not greatly affected

Question 14

How are anticyclones formed as a result of poleward extensions of subtropical high pressure cells.

Answer 14

• Hadley cells
• 30 degrees north and south, there is a sub tropical high pressure belt where cold air is sinking and where little clouds occur.
• zone of max heating is the itcz
• northern summer, itcz, moves northwards and so does the Hadley cell with the subtropical high pressure belt.
• high pressure cells of North Atlantic and North African closer o British Isles.
• come under influence of these subtropical high pressure belts.