Download Weather and Climate - Channel 4 Learning

Introduction
We see the outcome of the weather all around us,
C O N T E N T S
all the time, but the processes at work cannot be
seen. As a result, any understanding of what is
Programme 1
happening to the air around us requires an
The Air Around Us
explanation of abstract ideas.
This unit of five 20-minute programmes has been
made by the Dutch television station N.O.T. The
programmes explore and demonstrate the key
physical processes affecting weather and climate
and, in order to explain the fundamental concepts
covered in the unit, a combination of graphics,
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Programme 2
Differences in Temperature
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Programme 3
Why Does it Rain?
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Programme 4
Climates in the Tropics
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three-dimensional imagery and large scale models is
Programme 5
used.
Climates in Europe
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The programmes are set in a variety of locations to
Credits
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show examples of weather and climate in closer
detail in different parts of the world. These include
Subtitles
All Channel 4 series for schools are subtitled on
Teletext for the deaf and hearing-impaired.
Bali, Tunisia, Iceland, Spain and several places in
Europe which experience a northwest European
climate.
Geographical Eye as a series looks at significant
geographical themes, usually through the
experiences of individuals or communities. It is
hoped that, as a result, pupils will be able to
appreciate the ways in which seemingly distant and
sometimes abstract ideas and issues affect the lives
of ordinary people.
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THE AIR AROUND US
The Air Around Us
What is weather?
The air is all around us. So is weather and we cannot escape from it. Even when we are indoors it affects
us – we have to have the heating on, draw the curtains or open a window. When we are outside, it affects
what we wear, what we can do and where we can go. For some people, the weather is very important.
Think about how it can affect a farmer, a long-distance lorry driver or the owner of a holiday hotel, for
instance.
Weather is made up of all the air (or atmospheric) conditions that exist at any one time at
any one place.
W E AT H E R A N D C L I M AT E
Task A
Look at these things that people say about the weather:
I can hardly see
my hand in front of
my face.
It’s pouring down.
What a nice
sunny day.
It feels very
muggy today.
It’s a bit chilly.
There’s a gale
blowing outside.
÷ Can you add more sayings to this list?
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Try matching each one of these comments with one of these weather conditions:
PROGRAMME
◆ Precipitation (rain, snow, sleet, drizzle, dew – that is, all forms of water which fall from the sky)
◆ Temperature (the heat or cold within the atmosphere)
◆ Humidity (a measure of how wet the air is)
◆ Wind strength and direction (the movement of the atmosphere)
◆ Cloud cover (the amount of sky covered by cloud)
◆ Visibility (the distance you can see or the clearness of the air)
Now we know what the weather is, let’s look at what it’s like today. One thing about the weather is that it
is always changing. There is always something interesting to observe and measure. We can also record how
it is changing and how it is different from place to place. The weather can be different even between two
sides of a building!
Task B
Use the list of headings below to observe the weather today. Write a short sentence for each heading.
Precipitation
Temperature
Humidity
Wind strength and direction
Sunshine
Cloud cover
Visibility
÷ Make a note of how the weather has changed through the day, from morning to afternoon.
Make up a vocabulary table of weather words used by your class, starting off with the words used in
your description of today’s weather and then adding others after thinking about the different seasons.
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THE AIR AROUND US
Measuring the weather
Task C
We often talk about ‘bad’ and ‘good’ weather. By ‘bad’ we usually mean wet and cold; and by ‘good’ we
mean dry and sunny. But what is good weather for some can be bad for others. Look at these headlines
about the same weather.
LONG HOT DRY SPELL DRAWS RECORD HOLIDAY CROWDS.
LONG HOT DRY SPELL LEADS TO WATER SHORTAGES
W E AT H E R A N D C L I M AT E
Try writing two versions of these two headlines.
BLIZZARDS IN NORTHERN SCOTLAND...
...AS HEAVY RAIN ENDS DROUGHT
If you were to compare your observations of today’s weather with those made by other people in your
class you will find you do not agree with each other. What one person describes as ‘cool’ another may
describe as ‘freezing’.
Task D
The weather is measured using instruments rather than our own judgement:
◆ Temperature is measured using thermometers.
◆ Precipitation is recorded using a rain gauge every 24 hours.
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◆ Humidity is measured using a hygrometer which has two thermometers.
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◆ Wind speed is measured using an anemometer.
◆ Wind direction is measured using a wind vane.
◆ Sunshine is measured using a sunshine recorder. This uses a lens to focus the sun’s rays on to a card.
◆ Cloud cover is usually estimated by eye.
◆ Visibility is estimated by using local landmarks.
Find out in more detail how each of these features of the ‘weather’ is measured. For example, how
do you use an anomometer to measure wind speed.
Increasingly, measurements are taken by using electronic sensors, computers and weather satellites. You
have probably seen weather satellite images on television.
Climate
We can use the measurements taken every day to build up a picture of the weather for a whole year and
from year to year. The end result is a picture of the average weather of a place – its climate.
In some parts of the world the weather stays the same for days on end. In the tropical forests it is hot and
wet nearly every day. In the Antarctic it is very cold and quite dry all the time. In these places the weather
is very much like the climate. In the United Kingdom though the weather changes from day to day;
however, we do have a rough idea of what the weather is going to be like from season to season.
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THE AIR AROUND US
Task E
÷ Look at the graphs below showing the weather records for 1992 at Malham Tarn Field Centre in the
Yorkshire Dales. They show average temperature, total sunshine and rainfall for each month. They do not
tell you what the weather was like on any one day. They show the climate for the whole year.
Sunshine
260
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
240
220
Sunshine (hours)
W E AT H E R A N D C L I M AT E
Temperature (°C)
Temperature
200
180
160
140
120
100
80
60
40
20
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Months (1992)
Rain
1
200
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180
160
Rain (mm))
140
120
100
80
60
40
20
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
M
th (1992)
Look at the temperature graph. Which month has the highest temperature and what is the
temperature? Which month has the lowest temperature and what is the temperature? What is
the difference in temperature between these two months? (This is called the annual range of
temperature).
Look at the rainfall graph. Which months have the highest rainfall? Which month has the lowest
rainfall? What is the total rainfall for the year?
Look at the sunshine graph. Which month has most sunshine and how many hours? Which month
has least sunshine and how many hours?
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Use these climate graphs for Malham Tarn to describe what the weather was probably like there in
the winter, spring, summer, and autumn 1992. Remember to use the vocabulary you built up, but now
you can use actual figures to be more accurate.
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THE AIR AROUND US
Explaining the weather
The heat from a fire or radiator warms up the air. Warm air rises, causing air currents which begin to
move around the room, as shown in Diagram 1 below.
Diagram 1
Cooling
Warm
Cold
W E AT H E R A N D C L I M AT E
Cool
Cold
On a bigger scale, this effect can cause breezes over land and sea, as shown in Diagrams 2 and 3. In this
case, though, it is the sun which is the source of heat.
Day time winds
Night time winds
air cools down and sinks
warm air rises
cool air moves out
cool air moves in
beach
beach
land heats up
sea
cold land
warm sea
Diagram 2
Diagram 3
F
Sun's rays
Equator
E
Sun's rays
Diagram 4
Thickness of the atmosphere
(not to scale)
PROGRAMME
North Pole
1
On a much bigger scale still, the same effect is responsible for the differences in climate between different
parts of the world.
Diagram 4 shows that the sun heats up places near the Equator
more than places near the poles because a) the same amount of
the sun’s energy is spread out over a much bigger area at the poles
than at the Equator; and b) the sun’s energy also has to pass
through a thicker layer of the atmosphere at the poles. These
differences create air currents which carry heat away from the
Equator. This movement of air produces the winds which also
carry moisture from sea to land and bring rain to different places.
÷ The sun’s energy is trapped in the atmosphere. The atmosphere lets sunlight in, but slows down the
escape of heat into space (rather like a greenhouse). One of the gases in the atmosphere, carbon dioxide is
especially good at trapping heat, and gradually the amount of carbon dioxide is increasing as we burn more
and more wood, coal and oil. The earth is warming up due to the greenhouse effect and this effect is
happening on a global scale.
Task F
Choose a number of sites around your school or home. Answer these questions about each of them.
◆ Is it sheltered or exposed?
◆ Which direction does it face: north, south, east or west?
◆ Is it a shady or sunny spot?
◆ Is it close to, or far from, buildings?
◆ What kind of ground is it on?
÷ Now, at each site, observe and measure the weather.
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D I F F E R E N C E S I N T E M P E R E AT U R E
Differences in Temperature
Have you noticed that during fine weather in summer the sky is often quite clear in the morning? Then, as
the sun gets higher in the sky, white fluffy clouds start to appear. They are forming over hot spots which
the sun has warmed up. Hot air rises taking with it water vapour which cools at higher levels to form
clouds.
At the Equator, the sun shines steeply down on the earth’s surface – much more steeply than at the poles.
It is not surprising that temperatures are hottest at the Equator. These high temperatures mean that air is
rising near the Equator. However, if hot air is rising, cooler air must be coming in to take its place. This
happens on a large scale across the globe and it is this action which produces the winds which flow across
the earth’s surface.
Task A
os
ph
e
er
W E AT H E R A N D C L I M AT E
Cold air sinking
at the Pole
m
At
Diagram 1 shows part of the earth’s
surface. Copy it and draw arrows to
show how the atmosphere should be
circulating as a result of high
temperatures near the Equator and
low ones. A start has been made for
you.
Unless you are an expert meteorologist,
you may have shown winds blowing
towards the Equator and air flowing back
to the poles high in the atmosphere. The
picture is much more complicated than
this for two reasons:
Diagram 1
Hot air rising
at the Equator
◆ the rising air cools and sinks long before it reaches the poles
◆ the rotation of the earth means the winds are deflected.
PROGRAMME
2
Diagram 2 shows the pattern of winds in the northern hemisphere. Notice that the British Isles lie in a belt
of winds which blow from the southwest. In winter they are also affected by cold winds from the poles.
Diagram 2
North Pole
The British Isles
Equ
ato
r
Direction of earth's rotation
Ideal wind direction
Actual wind direction
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D I F F E R E N C E S I N T E M P E R E AT U R E
Moving Water
The Scilly Isles are about 40 kilometres from Lands End out in the Atlantic (find them on a map of the
British Isles). They are famous for their daffodils which flower as early as January. They are sent for sale on
the mainland where there may be frost and snow still on the ground.
Task B
Map 1 shows the January isotherm for 0º over western Europe. Which of these statements is true?
◆ In western Europe, temperatures in January get lower the further north you go.
◆ In western Europe, temperatures in January get lower the further you go from the Atlantic Ocean.
Write a few lines about each statement using information from the map to help you.
Map 1
W E AT H E R A N D C L I M AT E
Arctic Circle
0°C
0°C
PROGRAMME
2
Scilly Isles
The shaded area has an average January temperature below 0°C
Task C
The direction of the wind has an important effect on our weather. For a period of days, say ten but the
more the better, record the direction of the wind and the temperature. Use a table like this:
DAY
WIND DIRECTION
T E M P E R AT U R E
Day 1
Day 2
The best time of the year to do this might be spring or autumn when we tend to get changeable weather.
You should take your readings at the same time each day, say lunch time. You may get more interesting
results if you take readings several times a day. That way you may spot a sudden change in wind direction.
Before you start, discuss what results you would expect. At the end of your observations, check whether
or not you were correct.
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D I F F E R E N C E S I N T E M P E R E AT U R E
Task D
÷ Why is it that countries in mainland Europe have much colder winters? An atlas map will show you that
the southwest winds blowing across the Scilly Isles come from the Gulf of Mexico where the sea is very
warm. As they blow across the sea, the winds drive the warm water northeastwards. It is this current of
warm water that keeps Britain and the coasts of Europe warmer than places further inland. However,
currents can also bring cold water from polar seas. The Labrador current carries cold water southwards
past Newfoundland in eastern Canada, giving it a colder climate than places across the Atlantic in Europe.
Try this experiment. You will need two tin cans, one full of water, one full of dry sand. Heat the two
tins gently by standing them in a saucepan of hot water. Record the temperature of the water and
the sand frequently and plot your results on a graph.
◆ What do you notice about how the water and sand heat up and cool down?
◆ Imagine your two tins are the ocean and the land. What do these results tell you about the differences
between the heating and cooling of land and sea?
W E AT H E R A N D C L I M AT E
Task E
Map 2 shows the sea level isotherms (lines of equal temperature) for January over the British Isles.
◆ Where is the warmest place in the British Isles in January?
◆ Which parts of the British Isles are warmer than 4ºC in January?
◆ Where is the coldest part of Ireland?
Use your knowledge of the way in which
water heats up and cools down and of the
currents in the Atlantic Ocean to help
you explain the information on the map.
Map 2
4
5
3
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2
Britain is often affected by low pressure
systems or depressions, which pull in air from
all around us. Because this air comes from
different parts of the northern
hemisphere, it has different
temperatures and humidity. This
gives Britain its ever
changing weather.
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5.5
3.5
5
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3.5
4
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5
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D I F F E R E N C E S I N T E M P E R E AT U R E
Map 3
Task F
Greenland
Am
Iceland
Pm
Pm
Pc
Pm
Tc
Am
Pm
Pc
Tc
Tm
Arctic maritime
Polar maritime
Polar continental
Tropical continental
Tropical maritime
Tm
North Africa
W E AT H E R A N D C L I M AT E
Look at Map 3
showing some of
the different
kinds of air,
called air
masses, which
affect Britain.
Depending on
where they have
come from and
the time of year,
they will bring
cold, mild, warm,
hot, wet or dry
weather.
Using Map 3 to help you, complete a copy of this table. One has been done for you.
AIR MASS
Pc
W I N T E R W E AT H E R
S U M M E R W E AT H E R
cold and dry
hot and dry
Am
Pm
Tc
Tm
High pressure is stationary over the British Isles and the spell of fine weather will continue.’
PROGRAMME
2
High pressure areas are a mass of heavy air. They are difficult to move and so can last for days and even
weeks. In the high pressure, air sinks and light winds flow outwards. This keeps out air which might bring
rain from the sea. Because the air is sinking it is also getting warmer so no clouds form. In summer this
gives long hot spells and often leads to drought conditions. In winter high pressure is linked to frosty
nights. Can you think why this is so?
Good and bad weather
So Britain’s weather is very changeable and depends on the season, the wind direction, the air pressure and
whether we live close to the sea or not. We often talk about good or bad weather but what do we mean?
Different people mean different things. Hot dry weather is often described as “good” but after a long dry
spell some people would prefer to have a downpour!
Task G
Make a table of your own like the one below to show how people might have different views about the weather.
W E AT H E R
GOOD
BAD
Snowy
Skier
Lorry Driver
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WHY DOES IT RAIN?
Why Does it Rain?
Water everywhere
Water is essential to life. Without it there would be no life on earth. The earth is a wet planet with 70% of
it covered by oceans and seas. The Pacific Ocean alone is bigger than all the continents put together. 97%
of all the earth’s water is found in the oceans. Where is the other 3%. Diagram 1 tells us.
Condensation
W E AT H E R A N D C L I M AT E
Atmosphere
0.0001% of water
Precipitation
Evaporation
Ice 1.9%
Lakes 0.009%
SEA
97% of all water
LAND
Groundwater 1.9%
Diagram
Cycle
Diagram 11 The
TheEarth’s
Earth'sWater
Water and
and Water
Water Cycle
Notice that water is always on the move as:
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◆ falling as precipitation to the ground
PROGRAMME
◆ water vapour in the atmosphere being carried along by the wind
◆ flowing over the land in rivers and glaciers
◆ passing underground through soil and rocks
◆ Eventually the water finds its way back to the oceans. This movement of water is called the water
(or hydrological) cycle.
Why does it rain?
Task A
When hot air meets cold air or a cold surface, moisture droplets form to make a mist or cloud. This
cooling of moist air to form a cloud of moisture droplets is called condensation and it happens when:
◆ you breathe out on a cold day
◆ hot air comes out of a kettle spout
◆ you breathe on to a cold window.
÷ Can you think of any other examples?
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WHY DOES IT RAIN?
We have seen how the cooling of moist air to form a cloud of moisture droplets is called condensation.
How does this happen naturally to form mists or clouds?
Task B
Mist or haar forms
W E AT H E R A N D C L I M AT E
In the northeast of England in spring, mists often form along the coast when a breeze blows in from the
North Sea. The coasts sometimes can be blanketed in a fog, called the Haar, while only a little way inland
the sun is shining. The diagram below shows what happens.
Easterly wind chilled over sea
Sun dries up mist
North East Coast
Cold North Sea
Diagram 2
Diagram 2
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3
Inland mists often form in hollows after a cold night as shown below.
Hill tops clear
Layers of mist form
Clear night sky lets heat escape
Cold heavy air sinks into valley
Diagram
Diagram 33 Inland mists often form In hollows after a cold night
◆ In what way might the Haar be a hazard on the northeast coast of England?
◆ Why might patches of mist be a hazard after a cold night?
◆ Why can hilltops be sunlit in the early morning while valley bottoms are covered in mist? Use Diagram
2 to help you.
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WHY DOES IT RAIN?
Different kinds of rain
For it to rain there needs to be a supply of moist air and something to cool it for condensation to take
place. Even then, rain will only fall if the tiny drops of moisture collect into bigger drops which are too
heavy to be held up by the air.
Task C
W E AT H E R A N D C L I M AT E
Clouds and rain are formed as a result of air rising and cooling as it reaches higher levels. Diagram 4 shows
the three main ways in which this happens. Make your own copy of the diagrams and use the descriptions
to label each one.
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Convectional rain falls when the hot sun warms
the ground and surface layers of air. The warm
air rises and, as it meets cooler air, is cooled
itself. Above a certain height the air becomes
cold enough for condensation to take place and
cloud begins to form. The rising current of air
produces a tall cumulus cloud, and when the
water droplets are big enough, rain begins to fall.
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Relief rain takes place where moist air currents,
such as winds off the sea, rise over high ground.
The rising air is cooled and clouds form to
produce rain. By the time the winds have passed
over the high ground, they have lost much of
their moisture. As they descend, they become
warmer and drier so no rain falls. This dry side
of the high ground is called a rain shadow area.
Sea
Front
Cold air
Warm air
Diagram 4
Diagram 4
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Frontal rain forms where cold air meets warm
air along a front. The cold air is heavier than the
warm air and the warm air rises over it just as it
would over a range of hills. The warm air is
cooled, cloud forms along the front and rain may
fall.
C L I M AT E S I N T H E T RO P I C S
Wet and dry places
Task D
Singapore, southeast Asia
2,413 mm
Goias, Central Brazil
1,646 mm
In Salah, Southern Algeria
15 mm
Lisbon, Portugal
686 mm
Cape Town, South Africa
508 mm
Medicine Hat, Alberta, Canada
325 mm
Charleston, South Carolina, USA
1,205 mm
Osaka, Japan
1,336 mm
Shannon, Western Ireland
927 mm
Berlin, Germany
609 mm
Eismitte, Central Greenland
110 mm
W E AT H E R A N D C L I M AT E
This table shows the precipitation totals for weather stations around the world. The amount of rain
places receive varies enormously from 15 mm to 2,413 mm. Use a ruler to compare these two
amounts.
Use an atlas map to locate the places listed in the table. Are these statements true?
◆ Places a long way from the coast are drier than places near to it.
◆ Places near to the Equator are wetter then places a long way from it.
cross mostly west to east
Westerly winds
Atlantic
Ocean
Ireland
PROGRAMME
Fronts
4
For one or two of the places in the list, try to suggest why it has a wet or dry climate. For instance
from what you already know about the British Isles’ climate you could explain the rainfall at Shannon
in Western Ireland.
Irish Sea
Warmest summers
Western
uplands
North Sea
Eastern
lowlands
Diagram
Diagram 55
Here is a simple cross section across the British Isles. This country is affected by convectional, relief, and
frontal rain. Different kinds of air mass cross it, sometimes bringing moist air and sometimes dry air.
Task E
Study this section alongside a map of the British Isles.
Where would you expect most relief rain to fall?
Which part of the country might get most convectional thunderstorms?
Would frontal rain affect one region more than another?
Do you live in a wetter or drier part of the British Isles. Write a brief description of the climate
in the part of the country where you live.
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C L I M AT E S I N T H E T RO P I C S
Climates in the Tropics
At the Equator, the sun is always high in the sky during the day. It is right overhead on or around 21 March
and 21 September.
Task A
Climate graph for Uaupes (Amazonia)
Look at the graph showing the climate in the
Amazon Basin near to the Equator.
Total rainfall 2680 mm
Temperature
Rainfall (mm)
500
◆ 25ºC is the temperature of a hot summer’s
W E AT H E R A N D C L I M AT E
day in the British Isles. Would you say that
there is a winter and a summer in the
Amazon Basin?
30
25
400
20
300
15
200
10
100
Temperature (°C)
◆ What is the difference in temperature
between the hottest and the coldest month?
(This figure is called the range in
temperature.)
35
600
5
0
0
Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov Dec
Month
◆ London gets between 500 and 600 mm of rain each year. How does this compare with the Amazon
Basin?
◆ In the British Isles it is possible to recognise seasons, in particular a wetter and colder winter, and a
drier warmer summer. How would you describe ‘seasons’ in the Amazon Basin?
Tropical rainforest grows in the hot wet climates found near the Equator. Because it is hot and wet all year
round, the forest is evergreen with some plants shedding their leaves while others are flowering or coming
into leaf. In the heat, a lot of the rain which falls does not run into the rivers but returns to the
atmosphere.
Tasks B
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4
This table shows what happens to the rain that falls in the rainforest.
Transpiration (given off by leaves as water vapour)
48.5%
Evaporation from the leaves as they dry
25.6%
Run-off in the rivers and streams
25.8%
Evaporation from the soil
0.1%
Total rainfall
100%
Use these figures to add labelled arrows to a copy of Diagram 1 (the rainforest vegetation) to show
the forest water cycle. Make your arrows of varying widths to show the different percentages.
Diagram 1
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Height (m)
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20
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C L I M AT E S I N T H E T RO P I C S
Notice in your diagram that the trees and plants of the rainforest are responsible for returning a large
amount of water to the atmosphere. Why is this?
◆ What would happen if the forest were cleared for agriculture or some other human activity?
◆ How would this affect the climate of the areas near the Equator?
Because the trees grow quickly in the rainforest, they produce three times as much weight of leaves as
a forest in Britain. On the forest floor, the dead leaves decay to form a plant food which keeps the trees
growing.
◆ What would happen if the trees were removed?
You can see that the forest is very important to the climate and the soils of tropical areas. Destroying it
W E AT H E R A N D C L I M AT E
could lead to climatic change and poor soils as well as the loss of the forest itself.
Seasonal rains
In Britain, well away from the Equator, summer is different from winter because it is warmer, but in the
tropics it is warm most of the year. If there are seasons at all, they are the wet and the dry season. Why
is this?
In the middle of summer in Britain, the sun seems to be high in the sky. It is at its highest on around 21
June. On that day at noon you would have a very short shadow. At the same time the sun is right overhead
at places along the Tropic of Cancer. There you would have no shadow at all or a very small one just
around your feet.
Tasks C
4
Here are some places are in the northern hemisphere, on or near the Tropic of Cancer. Find them
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on an atlas map.
◆ Dakha, Bangladesh
◆ Aswan Dam, Egypt
◆ Ahaggar Mountains, Central Sahara Desert
◆ Havana, Cuba
◆ The Island of Taiwan, Eastern Pacific Ocean
At all these places, the overhead sun brings very hot conditions in June – this means rising air, clouds and
the possibility of heavy rain. But it will only rain if the air is moist enough to start with.
Which of these places is close to or on the sea?
Which are most likely to get rain in June?
Find some more places on or near the Tropic of Cancer and decide whether or not they are likely
to get rain in June.
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C h a n n e l
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Te l e v i s i o n
C o r p o r a t i o n
C L I M AT E S I N T H E T RO P I C S
When the sun is over the Tropic of Cancer in June, air is drawn in from north and south as hot air rises. If
the air is moist it will bring rain. In West Africa, for example, coastal areas get quite heavy rain but as the
winds pass inland they bring less and less precipitation.
When the sun is overhead at the Tropic of Capricorn in the southern hemisphere in January, there is no
rain away from the coast in West Africa. So in the inland regions of West Africa, known as the Sahel, all life
depends on the seasonal rains. If they fail, then crops and animals may die, wells run dry and people have to
move to wetter areas or seek aid.
Task D
W E AT H E R A N D C L I M AT E
Map 1 shows part of northern Nigeria. It shows the rainfall, dams for storing water and places where
water is used for irrigation.
N
NIGER
50
0m
Lake Chad
m
au
iss
rM
ve
Maiduguri
Ri
Ri
ve
rK
ala
gu
Kano
jia
Hade
m
River
NIGERIA
KEY
1000m
Tiga Reservoir
4
International Boundary
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Dadin Kowa
Reservoir
Rainfall in millimetres
City
Bauchi
Dam site
Irrigation scheme
0
Proposed irrigation scheme
100km
Seasonal marshes
Map 1Rainfall
Rainfall
and
irrigation
schemes
in part
of northern
Nigeria
and
irrigation
schemes
in part
of northern
Nigeria
÷ Use the map to answer these questions.
◆ What are the wettest and driest areas?
◆ Where are the reservoirs and irrigation schemes found?
◆ Why are they there?
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Ch a n n e l
Fo u r
Te l e v i s i o n
C o r p o r a t i o n
C L I M AT E S I N E U RO P E
Climates in Europe
Map 1 is a typical weather map for Europe in spring. It is like the ones you see sometimes on TV or in a
newspaper. On it you can see isobar lines of equal air pressure in millibars, fronts (where warm and cold
air meet) and letters to show where pressure is high (H) and low (L). The arrows show how the winds are
spiralling around an area of low pressure.
This could be how a weather forecaster would describe the map: ‘A belt of high pressure extends from the
mid Atlantic across North Africa and the Mediterranean Sea. Further north, a low pressure area is moving
eastwards towards the British Isles, accompanied by a series of fronts. Northern Europe is dominated by
high pressure. As the low pressure moves eastwards, the south-westerly winds now over the British Isles
W E AT H E R A N D C L I M AT E
will be replaced by northerly gales.’
Why is this so typical in Europe in spring? Let’s work out first why the areas of high and low pressure form
over northern Europe and north Africa.
The high pressure in northern Europe is a result of air cooling over the Arctic. Cold air is heavy air. It
sinks, giving high pressure and flows southwards as winds. The high pressure over North Africa is air which
starts out as warm air over the Equator, has risen and then cooled to sink back down over North Africa.
From here, it spreads out either back to the Equator or northwards towards Europe.
So, Europe is sandwiched between cold air from the north and warmer air from the south. On the map
you can see that when two different kinds of air meet, they swirl around like water going down a drain.
Depending where you are, you will get cold air from the poles or warm air from the south. That is why
British weather is so changeable.
The fronts on the map show where cold air meets warm air. Where this happens, rain is likely because the
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5
lighter warm air rises over the heavier cold air.
Task A
Look at Map 1 again. Use it to help you describe the weather that different places will be having.
Choose your own places. Remember that:
◆ winds from a northerly direction will be cold
◆ winds from a southerly direction will be warmer
◆ rainfall will occur close to fronts
◆ the swirling mass of air (a depression) shown on the map will move eastwards so the weather will
change as it passes over different places.
The map shows typical conditions on a spring day. In summer, everything moves north with the sun. If the
high pressure moves far enough north, Britain will get fine weather as will the Mediterranean. In winter,
the depressions are further south and pass over the Mediterranean area.
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Te l e v i s i o n
C o r p o r a t i o n
18
Ch a n n e l
Fo u r
Te l e v i s i o n
C o r p o r a t i o n
2
H
103
1024
H
10
24
32
10
© 2000
1016
1008
1000
992
984
976
968
L
L
L
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5
24
H
H
24
10
W E AT H E R A N D C L I M AT E
10
H
Winds
Occluded front
Warm front
Cold front
KEY
C L I M AT E S I N E U RO P E
C L I M AT E S I N E U RO P E
Task B
÷ Look at these climate graphs for four places in Europe.
°C
40
÷
°C
40
A
202m
30
30
20
20
10
10
B
107m
0
0
Temperature Range
21°
-10
-10
Temperature Range
18°
mm
250
mm
250
mm
250
200
200
200
200
150
150
150
150
100
100
100
100
50
50
50
50
0
0
0
J F M A M J J A S O N D
°C
40
°C
40
D
43m
30
20
20
10
10
0
0
Temperature Range
9°
-10
0
J F M A M J J A S O N D
C
50m
30
Rainfall 401mm
-10
-20
5
Rainfall 650mm
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mm
250
W E AT H E R A N D C L I M AT E
-20
-20
Temperature Range
15°
-20
mm
mm
250
mm
250
200
200
200
200
150
150
150
150
100
100
100
100
50
50
50
50
0
0
250
Rainfall 826mm
0
J F M A M J J A S O N D
mm
250
Rainfall
2002mm
0
J F M A M J J A S O N D
Compare graphs A and B.
÷ Which place has the highest temperatures?
The answer is B: In summer, average temperatures almost reach 30ºC but at A they only reach about
20ºC. In winter, temperatures at A fall to freezing point, so B is warmer all year round.
÷ Which place gets the most rainfall and when does it fall?
The answer is A: It gets almost 250 mm more rain than B with most of it falling between May and
August. On the other hand, the wettest season at B is the winter with most rain falling between November
and February.
These answers tell us that B is warmer than A and is therefore likely to be further south. B is drier than A
and gets its rain in winter.
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Te l e v i s i o n
C o r p o r a t i o n
C L I M AT E S I N E U RO P E
Task C
W E AT H E R A N D C L I M AT E
Map 2 shows the four places represented by graphs A, B, C, D in Task B. Work out which graph matches
which place.
2
1
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5
3
0
km
4
800
Map 2
Here are some clues to help you:
◆ Places a long way from the sea warm up quickly in summer but cool down quickly in winter giving them
a wide range of temperature.
◆ Warm currents of water in the Atlantic Ocean flow northeastwards towards Europe keeping coastal
places mild in winter.
◆ Places near to the Atlantic Ocean are affected by moisture-bearing winds.
◆ Depressions and fronts move towards Europe from the west.
◆ These depressions also pass over the Mediterranean Sea in winter.
Place 1 = Graph
Place 3 = Graph
Place 2 = Graph
Place 4 = Graph
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Te l e v i s i o n
C o r p o r a t i o n
B
Credits
Produced by: N.O.T. Holland
Commentary: Phil Griffin
English Scripts: Bob Drew, John Austin
Study Guide written by Keith Orrell
Study Guide edited by John Austin
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