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19 Cards in this Set

  • Front
  • Back

Name the three anticyclones that affect South Africa.

South Atlantic anticyclone


Kalahari anticyclone


South Indian anticyclone

Along which line of latitude are the anticyclones located?

30 degrees South

Explain why anticyclones bring clear skies and sunshine.

- Anticyclones bring descending, dry, warming air resulting in clear skies and sunshine.


- Most of South Africa is dominated by this type of weather.


- An anticyclone in the Southern hemisphere has winds blowing around the high in an anticlockwise direction.

How do the South Atlantic, South Indian and Kalahari anticyclones affect South Africa's climate all year round?

- They cause descending warming air and dry conditions for most of the year.


- Due to their positions changing, this gives us changing seasonal climate and changing weather conditions.

Name four characteristics of the South Atlantic High Pressure.

- Located on South Atlantic


- Anticlockwise circulation causes onshore south-westerly winds blowing over SA's West coast.


- Dry stable air coming from a cooler latitude


- No precipitation occurs.

Discuss the characteristics of the South Indian High Pressure.

- Lies over South Indian Ocean.


- Anticlockwise circulation cause onshore north-easterly winds blowing over South Africa's east coast.


- Air is hot and unstable


- Sometimes when the inversion layer is above the escarpment light rain in the plateau region can be expected.

What are the characteristics of the Kalahari High Pressure.

- Lies over northern parts of South Western Africa


- Located in upper layers at 6000m


- Air heats up as it descends by 1C for every 100m drop


- the hottest low and it causes inversion conditions.

How do the anticyclones move in summer and winter?

Summer:


- Tropical depression (Tropical cyclones)


- Moisture front and line thunderstorms


- Cut-off low


- South easterly wind




Winter:


-Frontal depressions (Mid-latitude cyclones)


- South African Bergwind


- Coastal low pressure

How do anticyclones affect SA's weather in winter?

- When it is winter in the Southern hemisphere, the sun is directly overhead in the Northern hemisphere, which causes the heat distribution and pressure belts to shift northwards.


- South Indian & South Atlantic anticyclones have moved closer to the coast.


- Winds blowing out these anticyclones have a shorter distance to travel across the sea before they reach the land, therefore, they pick up less water vapour and bring less rain at this time of year.

Explain the weather conditions in the interior during winter.

- the interior experiences clear skies, sunny weather, no rain.


- Temperatures: freezing in the morning, high 20's midday.


- These weather conditions are caused by the Kalahari anticyclone.

Discuss the position of the Kalahari anticyclone in winter

Discuss the position of the Kalahari anticyclone in winter

- Very cold air immediately above the plateau


- dry air from the Kalahari anticyclone warms up as it subsides.


-Above the plateau there is a layer of air in which the temperature increases with height (Inversion layer). Rising air cannot penetrate the inversion layer.


- Warm moist air from the Indian ocean cannot blow onto the plateau because it is blocked by the inversion layer, therefore, winter is in drought in the interior in SA.

Define the term inversion layer

a layer of air where temperature increases with increasing altitude.

Describe how each of the three anticyclones that affects South Africa moves between summer and winter (6)

Summer

- During Summer, the Kalahari anticyclone has risen vertically by about 500m

- It is very hot in the interior.


- the hot air rises causing low pressure at the surface.




.

Explain why the interior of South Africa get rain in summer

- the inversion layer rises with the anticyclone allowing moist air from the Indian Ocean to penetrate inland (this is why we have rain in the summer)

In the summer the South Atlantic anticyclone moves in which direction, and what is the result?

- it moves south, it often elongates and forms a ridge south of the country.


- this produces strong southeasterly winds over the Cape Peninsula and Southern Cape


-When the winds reach the land, they are funneled between mountain ranges, down valleys, etc which can cause gale force winds.

What are travelling disturbances?

Some weather patterns that arise from the South Atlantic, South Indian and Kalahari anticyclones only occur at certain times of the year, and travel from one area to another.

Explain what a moisture front is

a zone extending from northwest to southeast through the interior of South Africa.


Warm, moist northeasterly winds from the Indian Ocean converge with cooler winders from the southwest.

What are line thunderstorms?

- the warmer air is unstable and rises to great heights along the front. The air cools, reaches dew point, condensation occurs and tall cumulonimbus clouds develop, accompanied by thunderstorms, hail and heavy rain.


- they occur along the line of the moisture front.


- they occur in the interior during hot weather, night and day


- can cause damage to crops and buildings.


- occur only if Kalahari anticyclone has risen to allow moist air to reach the interior

Discuss what a coastal low pressure system is.

- Coastal lows move west to east, during autumn and winter


- air circulation is clockwise and into the low, causing an onshore flow behind the coastal low, bring clouds and dog.


- ahead of the low there is an offshore flow causing clear warm weather - can create a fire hazard.