This is a summary about Sub-tropical Anticyclones based off of my textbook and slideshows that my teacher had sent to us.
The work is summarised in detail and diagrams and images are included in order to help you understand the work.
This summary covers both the IEB and CAPS curriculum.
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.
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