Anticyclones

Question 1

How are they formed?

Answer 1

• A descending air mass compresses and warms adiabatically.
• Relative Humidity decreases and condensation does not occur
• Cloud formation is suppressed, leading to dry conditions
• This subsistence means air is stable, leading to fine, dry weather
• Air moves clockwise (in the Northern Hemisphere) out from the High Pressure centre
• There is a low pressure gradient, meaning there are low winds
• Anticyclones are very slow moving and remain stationary for days

Question 2

Contrast the impacts of winter anticyclones and summer anticyclones on people for daytime temperature:

Answer 2

• In the winter the sun is low in the sky, reducing the amount of heat energy; the lack of cloud cover means heat escapes.
• In the summer the sun is high in the sky and the lack of clouds means more insolation reaches the earth’s surface

Question 3

Contrast the impacts of winter anticyclones and summer anticyclones on people for nighttime temperature:

Answer 3

• In the winter frost conditions occurs as heat escapes by radiation
• In the summer the lack of clouds means heat escapes, and nighttime temperatures drop

Question 4

Contrast the impacts of winter anticyclones and summer anticyclones on people for unique weather events:

Answer 4

• In the winter the Polar continental air from central Asia is cold, dry and stable. Upon reaching the North Sea it acquires warmth and moisture leading to snowfall.
• In the summer on hot days air rises by convection. It expands, cools and relative humidity increases and condensation occurs as dew point is reached. Thunderstorm clouds form.

Question 5

Compare how winter and summer anticyclones are similar

Answer 5

• They both have high pressure
• Both have dry conditions caused by sinking air warming adiabatically
• Both have shallow Pressure Gradients and therefore low wind speeds