Subtropical anticyclones
Anticyclone = large scale airmass rotating around strong centre of high atmospheric
pressure, cells of HIGH pressure
Subtropical = area lying between tropic of cancer; 40˚ N and tropic of Capricorn; 40˚S
South Africa lies between 22˚S and 35˚S and its climate is dominated by belt of
subtropical highs
South Africa has x3 anticyclones which form part of the belt of subtropical highs
1. South Atlantic anticyclone
2. South Indian anticyclone
3. Kalaharian (interior) anticyclone
Anticyclones move in an ANTICLOCKWISE direction in the southern hemisphere
(clockwise direction in the northern hemisphere)
Caused by subsiding air from tropical & mid-latitude pressure cells
Bring descending, dry, warming air = clear skies and sunshine
Most of SA is dominated by this weather
Descending air = warms adiabatically
Influence on climate in WINTER:
Move northwards (heat equator)
SIA (south Indian anticyclone) and SAA (south Atlantic anticyclone) move closer to
the coast, the winds blowing out of these cyclones have a shorter distance to travel
across the sea to reach the land and therefore pick up less water vapour = less rain
Weather in interior: clear skies, sunny weather and NO rain
- Temps range from freezing in morning to high 20s mid-day (continental climate)
- Often several months of drought; caused by KA (kalaharian anticyclone)
1. Very cold air immediately above plateau
2. Dry air from Kalaharian anticyclone warms up as it subsides
3. Above plateau there is a layer in which the temperature increases with height
= inversion layer
4. Rising air cannot penetrate inversion layer, warm moist air from Indian Ocean
cannot blow onto Plateau as it is blocked by the inversion layer = drought in
winter at interior
Influence on climate during SUMMER:
During summer, there is a HP over the sea and a LP on the land.
Anticyclone = large scale airmass rotating around strong centre of high atmospheric
pressure, cells of HIGH pressure
Subtropical = area lying between tropic of cancer; 40˚ N and tropic of Capricorn; 40˚S
South Africa lies between 22˚S and 35˚S and its climate is dominated by belt of
subtropical highs
South Africa has x3 anticyclones which form part of the belt of subtropical highs
1. South Atlantic anticyclone
2. South Indian anticyclone
3. Kalaharian (interior) anticyclone
Anticyclones move in an ANTICLOCKWISE direction in the southern hemisphere
(clockwise direction in the northern hemisphere)
Caused by subsiding air from tropical & mid-latitude pressure cells
Bring descending, dry, warming air = clear skies and sunshine
Most of SA is dominated by this weather
Descending air = warms adiabatically
Influence on climate in WINTER:
Move northwards (heat equator)
SIA (south Indian anticyclone) and SAA (south Atlantic anticyclone) move closer to
the coast, the winds blowing out of these cyclones have a shorter distance to travel
across the sea to reach the land and therefore pick up less water vapour = less rain
Weather in interior: clear skies, sunny weather and NO rain
- Temps range from freezing in morning to high 20s mid-day (continental climate)
- Often several months of drought; caused by KA (kalaharian anticyclone)
1. Very cold air immediately above plateau
2. Dry air from Kalaharian anticyclone warms up as it subsides
3. Above plateau there is a layer in which the temperature increases with height
= inversion layer
4. Rising air cannot penetrate inversion layer, warm moist air from Indian Ocean
cannot blow onto Plateau as it is blocked by the inversion layer = drought in
winter at interior
Influence on climate during SUMMER:
During summer, there is a HP over the sea and a LP on the land.
