Download 1.1 ocean current slides

CLIMATOLOGY
Factors Affecting South Africa’s Temperature and Rainfall:
OCEAN CURRENTS.
Port Nolloth
Durban
• Ocean currents are large masses of water that are
constantly moving in the world’s oceans.
• The main cause of ocean currents moving are:
1. winds;
2. differences in the water temperature and;
3. rotation of the earth.
WARM vs COLD OCEAN CURRENTS
• Water at the poles is cold.
• Water at the equator is warm.
• Nature corrects this imbalance by:
• Wind moving water on the surface of the ocean:
• Warm waters from the equator move towards the POLES ;
• Cold waters from the poles move towards the EQUATOR.
THE ATLANTIC OCEAN AND INDIAN
OCEAN.
SOUTH AFRICAS CURRENTS
Cold Benguela Current.
- Warm Agulhas Current.
-
EAST COAST OF SOUTH AFRICA:
WARM AGULHAS CURRENT.
1. The warm Agulhas current flows Southwards down the east
coast of Southern Africa.
2. These currents bring warm water from the Equatorial areas of
the Indian ocean to the east coast of South Africa.
3. The warm currents bring moisture which rise and form
water vapour: causing evaporation, condensation and
then rainfall.
4. This results in Durban experiencing warm summer and
warm winter temperatures.
5. Warm air holds more moisture than cold air.
WEST COAST OF SOUTH AFRICA:
COLD BENGUELA CURRENT.
• The cold Benguela current flows northwards up the west
coast of Southern Africa.
• These currents bring cold water from the polar regions of the
Atlantic ocean to the west coast of South Africa.
• The cold water cools the air above and sinks, making them
dry, NO moisture or heat.
• This results in Port Nolloth’s low summer and low winter
temperatures.
• Cold air holds less moisture than warm air.
Port Nolloth
Durban
BENGUELA CURRENT.
AGULHAS CURRENT.
• Moves North along the West
• Moves South along the East
coast of Southern Africa;
coast of Southern Africa;
• Feeds cold, dry air into the land
along the West coast;
• Therefore,
cooler.
temperatures
• Feeds warm, moist air into the
land along the East coast;
are
• Therefore,
warmer.
temperatures
are
PORT NOLLOTH
DURBAN
DISTANCE FROM THE SEA
(CONTINENTALITY)
• Land and water differ in their ability to absorb, transfer and
radiate heat energy.
Reflection is greater.
Less reflection,
More absorption.
Land heats up quickly,
WHY?
The sea heats up slowly,
WHY?
THE HEATING OF:
WATER vs LAND SURFACES.
WATER SURFACES
LAND SURFACES
• Heats up slowly.
• Heats up quickly.
• Retains heat.
• Looses heat quickly.
• Internal movement in water, distributes
absorbed energy.
• No currents to distribute heat.
• More evaporation and
absorbed as latent heat.
• Less reflection.
energy
is
• Less evaporation.
THE HEATING OF:
WATER vs SOLID OBECTS.
IMPORTANT TERMS:
TERM:
DEFINITION
EXAMPLE
Temperature
range
The difference between the MAXIMUM 40˚ - 10˚ = 30˚
and the MINIMUM temperatures.
20˚ - 16˚ =
Range
MAXIMUM – MINIMUM.
Maritime climate
Places along the coast have a maritime Durban, Cape Town, Richards Bay, Brazil,
climate because the sea air moderates the Portugal, Greece etc. . .
temperatures. They have a small
temperature range.
Continental
climate
Places far inland have a continental Johannesburg,
Pretoria,
Botswana,
climate because they have a big Zambia, Malawi, Bolivia, Slovakia, Belarus
temperature range. The further inland you etc. . .
go, the bigger the temperature range.
MARITIME vs CONTINENTAL
MARITIME
CONTINENTAL
• Coastal region.
• Inland region.
• Smaller temperature range between
summer and winter.
• LARGE temperature range between
summer and winter.
• Low temperature range less than 5˚C
• High temperature range greater than
10˚C.
• Warm summers, moderate winters.
• Warm/hot summer and very cold
winters.
WHY ARE THERE MARITIME AND
CONTINENTAL CLIMATES.
CONTINENTAL
MARITIME
• LAND SURFACES heat up more quickly,
• Air temperatures, over the ocean heat up
so IN SUMMER continental ( inland )
more slowly in summer and lose heat
regions
more slowly in winter.
experience
high
air
temperatures.
• IN WINTER, land surfaces lose heat more
quickly, therefore, cold temperatures.
• Therefore places close to the coast,
experience warm temperatures in summer
and moderate temperatures in winter.
HOMEWORK
• Entire of homework activity on page 11 of climatology booklet.
OCEAN CURRENTS
Cold Benguela current
• Cold Benguela current.
• Cools the air above it.
• Cold cry air blows onto the
land.
Port Nolloth
Durban
Warm Agulhas current
• Warm Agulhas current.
• Warms the air above it.
• Warm, moist air blows onto
the land.
• Therefore, warm temp at
Durban.
DISTANCE FROM THE SEA
(CONTINENTALITY)
Land heats up quickly
and loses heat quickly.
Less reflection,
More absorption.
Land heats up quickly,
WHY?
Reflection is greater.
The sea heats up slowly,
WHY?
REVISION: CLIMATOLOGY.
1. DIFFERENCE BETWEEN WEATHER AND CLIMATE.
FACTORS AFFECTING TEMPERATURE
1.
2.
3.
4.
LATITUDE.
ALTITUDE.
OCEAN CURRENTS.
DISTANCE FROM SEA ( CONTINENTALITY ).
WEATHER VS CLIMATE
1. ANGLE OF THE SUN’S RAYS
LATITUDE
Because of the shape of the earth, the sun’s rays strike the
earth directly (at 90 degrees) at the equator. Further away from
the equator, the sun’s rays strike at a lower angle.
2. SURFACE AREA HEATED
Where the sun’s rays strike the equator at 90 degrees, a small
surface area is heated, so heating is intense. The same
amount of sun’s heat reaching the poles is spread over a larger
surface area, so heating is less efficient, and temperatures are
cold.
3. AMOUNT OF ATMOSPHERE THAT THE SUN PASSES
THROUGH
As the sun’s rays pass through the atmosphere, some of its
heat is lost.
At the equator, the sun passes through less atmosphere, so
less heat is lost.
At the poles, the sun passes through more atmosphere so
more heat is lost before it reaches Earth.
ALTITUDE
WHY DOES TEMPERATURE
DECREASE WITH HEIGHT?
• As you increase in altitude, there
is less air molecules in the air.
• Therefore, there is less pressure
and gravity that is holding air
molecules closely together.
• Due to less air molecules further
up in the atmosphere, these air
molecules don’t absorb as much
heat, therefore it is colder higher
up in the atmosphere.
OCEAN CURRENTS
• HOW DO OCEAN CURRENTS
IMPACT AIR TEMPERATURE?
• Cold ocean currents ( from the
poles ) > cool the air above it >
wind blows cool air onto land >
therefore,
cold,
dry
temperatures.
• Warm ocean currents ( from the
equator ) > warms the air above
it > wind blows warm, moist air
onto land > therefore, warm
moist temperatures.
DISTANCE FROM THE SEA
• Water heats up slowly, and cools
down slowly. Therefore, coastal (
MARITIME CLIMATES ) have a
small temperature range between
summer and winter.
• Land heats up quickly and cools
down quickly. Therefore, inland (
CONTINENTAL CLIMATES ) have
a high temperature range between
summer and winter.
SLOPE ASPECT (TEXTBOOK PAGE 37)
• Aspect is the direction a slope is facing.
• This is important because it dictates the amount of sunlight an
area of land receives.
• This has a big impact on it's microclimate: whether it is
WARMER or COOLER, MOISTER or DRIER than
surrounding areas.
• This is important when investigating vegetation communities
or buying a block of land.
• In South Africa, land with a northerly aspect (NORTH FACING
SLOPE) will generally be warmer than land with a southerly
aspect. (SOUTH FACING SLOPE ).
WHERE DOES THE SUN’S RAYS HEAT
MORE DIRECTLY ON THE EARTH?
1. ANGLE OF THE SUN’S RAYS
Because of the shape of the earth, the sun’s rays strike the
earth directly (at 90 degrees) at the equator. Further away from
the equator, the sun’s rays strike at a lower angle.
2. SURFACE AREA HEATED
Where the sun’s rays strike the equator at 90 degrees, a small
surface area is heated, so heating is intense. The same
amount of sun’s heat reaching the poles is spread over a larger
surface area, so heating is less efficient, and temperatures are
cold.
WHERE DOES THE RISE AND SET?
1. ANGLE OF THE SUN’S RAYS
Because of the shape of the earth, the sun’s rays strike the
earth directly (at 90 degrees) at the equator. Further away from
the equator, the sun’s rays strike at a lower angle.
2. SURFACE AREA HEATED
Where the sun’s rays strike the equator at 90 degrees, a small
surface area is heated, so heating is intense. The same
amount of sun’s heat reaching the poles is spread over a larger
surface area, so heating is less efficient, and temperatures are
cold.
SLOPE ASPECT (TEXTBOOK PAGE 37)
• ASPECT refers to the compass direction that a slope faces. This will affect the angle at which the
sun’s rays strike a slope.
• FIGURE 2.5(a) EFFECT OF SLOPE ASPECT
ASPECT IN A IN THE SOUTHERN HEMISPHERE
FIGURE 2.5(b) EFFECT OF SLOPE
VALLEY
IN THE SHOUTHERN
HEMISPHERE:
THE NORTH FACING SLOPE.
Look at the north-facing slope in
Figure 2.5(a):
1. the sun’s rays strike the northfacing slope at 90°
2. there is a small surface area to
heat up
3. so heating will be effective
4. the north-facing slope will be
warm
in
the
Southern
Hemisphere.
IN THE SHOUTHERN
HEMISPHERE:
THE SOUTH FACING SLOPE.
Look at the south-facing slope in Figure
2.5(a):
1. the sun’s rays are striking the earth at
a lower angle (less than 90°)
2. there is a larger surface area to heat
up
3. so heating will not be very effective
4. the south-facing slope will be cool in
the Southern Hemisphere.
SOUTH FACING SLOPE
NORTH FACING SLOPE
WHICH IS THE SOUTH FACING SLOPE?
WHY?
In the Southern Hemisphere,
north-facing
slopes
are
warmer because they receive
more direct sun’s rays.
In the Northern Hemisphere,
the south-facing slopes are
warmer because they receive
more direct sun’s rays.
NORTH ; NORTH
EAST FACING
SLOPE.
North or north-east
facing properties are
considered the most
desirable because they
get the most direct
sunlight through the
day,
especially
in
winter when the sun is
at its lowest. In an
urban
area
where
sunlight is at a premium,
this can make a world of
difference.
EAST FACING
East-facing homes might
enjoy lovely sunrises and
full morning sun but that
will be over by noon. In
summer, mornings can
be uncomfortably warm
and in winter you won't
get much heat from the
sun at all.
SOUTH FACING
SLOPE.
You won't get much
sunlight at all from a
southerly aspect. Without
careful management your
house will most likely be
dark, with condensation
becoming a potential issue
that can cause mould and
mildew. But sometimes
you have to make this
work.
WEST FACING SLOPE.
West-facing
houses
(even
more
so
apartments) get the booby
prize for aspect. The
afternoon sun comes in
at an almost horizontal
angle
and
can
be
intense, particularly when
also reflected off water,
which can make for a very
uncomfortable summer.
HOMEWORK ACTIVITY ; PAGE 12.