Summary by: Kaylin Teneal
SUBTROPICAL ANTICYCLONES
LOCATION AND CHARACTERISTICS OF HIGH-PRESSURE CELLS
- Subtropical high-pressure belt: is found at 30° north and south.
- South African subcontinent are influenced by THREE cells:
o South Atlantic HP (SAHP)
o Kalahari HP
o South Indian HP (SIHP)
- Due to subsiding air, the land underneath them experience mainly fair, sunny and dry weather.
- These pressure cells are semi-permanent and move with the seasons.
o North in Winter
o South in Summer
CHARACTERISTICS OF HIGH-PRESSURE CELLS
- Air subsides at the centre, results in air warming and relative humidity decreases.
- Descending air
- Air that comes from the drier upper atmosphere
- Descending air warming at around 1°C
- Fair, sunny and dry weather conditions
- A continual state of change, eg. their size
- Moving northwards in winter, and southwards in summer
- Temperature inversion is the result of adiabatic warming
FACTORS INFLUENCING THE CLIMATE OF SOUTH AFRICA
1. Oceans surrounding the sub-continent
o Cold Benguela current brings cooler, dry air into the west coast.
o Warm Mozambique and Agulhas currents bring warm, moist air over the adjacent coastal
regions.
2. The plateau
o The high altitude of the plateau lowers temperatures.
o The steep escarpment along the coast preventing moist air coming into interior, drier
conditions are caused in the interior.
3. The subtropical anticyclones
, Summary by: Kaylin Teneal
o South Africa is situated in the subtropical high-pressure zone where air sinks and results in
higher temperatures and dry, cloudless weather.
SOUTH ATLANTIC HIGH-PRESSURE SYSTEM
- Situated far off the Namibian coast
- As air descends, it warms adiabatically
- Warm air lying over the cold ocean causes a permanent inversion and stable air
- South-westerly winds are common
o Caused by anticyclone circulation blowing towards the land
o These winds that blow towards the northeast tend to retain their moisture
o This causes dry conditions along the west coast of South Africa
SOUTH INDIAN HIGH-PRESSURE SYSTEM
- Tends to move away from the coast during summer, but moves nearer again in winter.
- The anticyclonic circulation causes north-westerly winds blowing over the eastern parts of South
Africa.
- As it blows over the warm ocean, it brings warm, moist and unstable air which may cause rain when
reaching the cooler land area.
KALAHARI HIGH-PRESSURE SYSTEM
- Slight weakening and southward displacement during summer.
- It's influence on circulation remains constant throughout the year.
- Is a towering three-dimensional system leaning slightly to the west.
- Does sink down (subside) in winter, and ascends in the summer months.
SUBTROPICAL ANTICYCLONES
LOCATION AND CHARACTERISTICS OF HIGH-PRESSURE CELLS
- Subtropical high-pressure belt: is found at 30° north and south.
- South African subcontinent are influenced by THREE cells:
o South Atlantic HP (SAHP)
o Kalahari HP
o South Indian HP (SIHP)
- Due to subsiding air, the land underneath them experience mainly fair, sunny and dry weather.
- These pressure cells are semi-permanent and move with the seasons.
o North in Winter
o South in Summer
CHARACTERISTICS OF HIGH-PRESSURE CELLS
- Air subsides at the centre, results in air warming and relative humidity decreases.
- Descending air
- Air that comes from the drier upper atmosphere
- Descending air warming at around 1°C
- Fair, sunny and dry weather conditions
- A continual state of change, eg. their size
- Moving northwards in winter, and southwards in summer
- Temperature inversion is the result of adiabatic warming
FACTORS INFLUENCING THE CLIMATE OF SOUTH AFRICA
1. Oceans surrounding the sub-continent
o Cold Benguela current brings cooler, dry air into the west coast.
o Warm Mozambique and Agulhas currents bring warm, moist air over the adjacent coastal
regions.
2. The plateau
o The high altitude of the plateau lowers temperatures.
o The steep escarpment along the coast preventing moist air coming into interior, drier
conditions are caused in the interior.
3. The subtropical anticyclones
, Summary by: Kaylin Teneal
o South Africa is situated in the subtropical high-pressure zone where air sinks and results in
higher temperatures and dry, cloudless weather.
SOUTH ATLANTIC HIGH-PRESSURE SYSTEM
- Situated far off the Namibian coast
- As air descends, it warms adiabatically
- Warm air lying over the cold ocean causes a permanent inversion and stable air
- South-westerly winds are common
o Caused by anticyclone circulation blowing towards the land
o These winds that blow towards the northeast tend to retain their moisture
o This causes dry conditions along the west coast of South Africa
SOUTH INDIAN HIGH-PRESSURE SYSTEM
- Tends to move away from the coast during summer, but moves nearer again in winter.
- The anticyclonic circulation causes north-westerly winds blowing over the eastern parts of South
Africa.
- As it blows over the warm ocean, it brings warm, moist and unstable air which may cause rain when
reaching the cooler land area.
KALAHARI HIGH-PRESSURE SYSTEM
- Slight weakening and southward displacement during summer.
- It's influence on circulation remains constant throughout the year.
- Is a towering three-dimensional system leaning slightly to the west.
- Does sink down (subside) in winter, and ascends in the summer months.
