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TOPIC THREE
WEATHER
and
CLIMATE
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Climate
what is climate?
Climate is the average weather usually taken over a 30-
year time period for a particular region and time period.
Climate is not the same as weather, but rather, it is the
average pattern of weather for a particular region.
What is our climate system
Atmosphere
The atmosphere covers the Earth. It is a thin
layer of mixed gases which make up the air we
breathe. This thin layer also helps the Earth
from becoming too hot or too cold.
Oceans
Oceans cover about 70 percent of Earth's sur-
face. Their large size and thermal properties
allow them to store a lot of heat.
Land Land covers 27 percent of Earth's surface and
land topography influences weather patterns.
Ice
Ice is the world's largest supply of freshwater.
It covers the remaining 3 percent of Earth's
surface including most of Antarctica and
Greenland. Ice plays an important role in regu-
lating climate, because it is highly reflective.
Biosphere
The biosphere is the part of Earth's atmos-
phere, land, and oceans that supports any liv-
ing plant, animal, or organism. It is the place
where plants and animals, including humans,
live.
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Types of climate:
There are lots of ways that scientists use to describe different
types of climate. One way is to divide up climates into five types:
tropical, dry, mild, cold, and polar. There are also important subcat-
egories including rain forest, desert, tundra, savanna, and steppe.
Why is climate important?
Climate can determine a lot of things, but it especially determines
what kind of plants and animals can live in an area. For example,
polar bears need a cold climate. They would be terribly hot and
would die quickly in the desert. When climates start to change, ani-
mals and plants become endangered.
Climate Change
Climates can change over long periods of time. Sometimes this is
just the cycle of the earth, but sometimes outside forces can have a
big impact on climate. Humans have had an impact by building large
cities and cutting down vegetation in places like the rain forest.
This has had an impact on the local climate. Other major events
that can affect the climate include volcano eruptions and changes in
the Sun.
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Fun Facts about Climate
a. Since the sun hits the land and ocean around the equator at a
direct angle, this area is generally the warmest area on the
planet.
b. Winds are generally in the same direction in certain places over
the oceans. They have names like the North East Trade winds and
Westerlies. These winds are important in climates and were also
important to ancient sailing ships which needed the power of the
wind to travel.
c. The wettest place on Earth is Mawsynram, Assam, India which
gets 467 inches of rain a year. The driest place is the Atacama
Desert, Chile which gets virtually no measurable rain on a yearly
basis.
d. The hottest place on Earth is the Denakil Depression in Ethiopia
where the average temperature is 34 degrees C (93 degrees F). The
coldest place is Plateau Station, Antarctica where the average
temperature is -56.7 degrees C (-70.1 degrees F).
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Over the history of the Earth there have been
times when the Earth's climate has cooled considera-
bly. During these times the ice cap, or glaciers, cov-
ering the North Pole has grown to encompass much of the northern
hemisphere.
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What is weather?
The weather is just the state of the atmosphere at any time, in-
cluding things such as temperature, precipitation, air pressure and
cloud cover. Daily changes in the weather are due to winds and
storms. Seasonal changes are due to the Earth revolving around the
sun
What causes weather?
Because the Earth is round and not flat, the Sun's rays don't fall
evenly on the land and oceans. The Sun shines more directly near
the equator bringing these areas more warmth. However, the polar
regions are at such an angle to the Sun that they get little or no
sunlight during the winter, causing colder temperatures. These dif-
ferences in temperature create a restless movement of air and wa-
ter in great swirling currents to distribute heat energy from the
Sun across the planet. When air in one region is warmer than the
surrounding air, it becomes less dense and begins to rise, drawing
more air in underneath. Elsewhere, cooler denser air sinks, pushing
air outward to flow along the surface and complete the cycle.
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WEATHER INSTRUMENTS
A THERMOMETER …………...measures the air
temperature. Most thermometers are closed glass tubes containing
liquids such as alcohol or mercury. When air around the tube
heats the liquid, the liquid expands and moves up the tube. A
scale then shows what the actual temperature is. Two types of
thermometers are used…the Minimum thermometer and the Maxi-
mum thermometer. One shows the lowest temperatures of the day
whilst the other shows the highest temperatures of the day. When
we take a temperature, we are measuring how hot or cold it is.
We measure the temperature using a thermometer. We change our
clothes based on the temperature. Farmers use the temperature to
know when to plant their crops and pilots use this to know
whether to de-ice their planes.
Did you know? The weather you see on the weather forecast is the
temperature in the shade.
A WIND VANE…….is an instrument that determines the
direction from which the wind is blowing.
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A SUNSHINE
RECORDER
….. records how
many hours of
sunshine shone
over a place in 24
hours.
A BAROMETER…...measures air pressure. It tells you whether
or not the pressure is rising or falling. A rising
barometer means sunny and dry conditions,
while a falling barometer means stormy and wet
conditions. An Italian scientist named Torricelli
built the first barometer in 1643.
A HYGROMETER measures the water vapour content of air or the
humidity.
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A HYGROMETER …..measures the water vapour content of air
or the
humidity.
A RAIN GAUGE……..measures the
amount of rain that has fallen over a
specific time period.
Rainfall…….
When people watch the weather forecast, they
want to know how hot/cold will it be and will it rain? Rain
is measured using a rain gauge.
Precipitation is any form of moisture falling to the ground.
It can be either: rain, sleet, hail, snow, freezing rain.
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STEVENSON’S SCREEN ……….or instrument shelter is a
shelter or enclosure to shield meteorological instruments
against precipitation and direct heat radiation from outside
sources, while still allowing air to
circulate freely around them.[1] It
forms part of a standard weather
station. The Stevenson screen holds
instruments that may include ther-
mometers (common, maximum and
minimum) and a hygrometer.
WEATHER BALLOONS….measure weather
conditions high up in the atmosphere.
VISIBILITY….. Visibility refers to how
far we can see and it is important for
transport users, namely, car drivers, ship
captains and airline pilots. When it is very
foggy, the weather agencies issue weather
warnings.
Visibility can be reduced by air pollution
but also, sandstorms, forest fires, blizzards and thunderstorms.
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An ANEMOMETER…. measures wind speed. The cups
catch the wind, turning a dial attached to the instrument.
The dial shows the wind speed. Wind can
be measured in kilometers per hour / miles
per hour or metres per second. The wind
direction is measured using a weather
vane and the four points of the compass.
Knowing the wind direction is important
because it helps give us clues as to what sort of weather
is coming. A wind from the north in the northern hemi-
sphere would be cold, and a wind coming from a sea or
ocean would be moist, with potential for rain.
WEATHER MAPS …indicate at-
mospheric conditions above a
large portion of the Earth's sur-
face. Meteorologists use weather
maps to forecast the weather.
Did you know? In the Arctic, the visibility is
often very good and it
can reach as far as 100
km
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WEATHER SATELLITES….
are used to photograph and
track large-scale air move-
ments. Then meteorologists
compile and analyse the
data with computers.
THE BEAUFORT SCALE…….
Devised by the Royal Navy in 1805, the Beaufort scale, is a meas-
ure of wind speed and is used to give guidance to ships in the
weather forecast as to what weather they can expect. In 1805, all
ships used sail for power and knowing what amount of wind was to
be expected and therefore how much sail could safely be deployed
was very important. Here we have a look at the Beaufort wind scale
in more detail.
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GREENHOUSE EFFECT and GLOBAL WARMING
The Earth is wrapped in a blanket of air called the 'atmosphere',
which is made up of several layers of gases. The sun is much hotter
than the Earth and it gives off rays of heat
(radiation) that travel through the atmosphere and
reach the Earth. The rays of the sun warm the
Earth, and heat from the Earth then travels back
into the atmosphere. The gases in the atmosphere stop some of the
heat from escaping into space. These gases are called greenhouse
gases and the natural process between the sun, the atmosphere and
the Earth is called the 'Greenhouse Effect', because it works the
same way as a greenhouse. The windows of a greenhouse
play the same role as the gases in the atmosphere, keeping
some of the heat inside the greenhouse.
THE NATURAL GREENHOUSE EFFECT..
The atmosphere has a number of gases,
often in tiny amounts, which trap
the heat given out by the Earth.
To make sure that the Earth's
temperature remains constant, the
balance of these gases in the
atmosphere must not be upset.
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The GREENHOUSE GASES are very important and are mainly:
water vapour ….occurs naturally in the atmosphere.
carbon dioxide ….produced naturally when people and animals
breathe. Plants and trees absorb carbon dioxide to live. Volcanoes
also produce this gas. Carbon dioxide is not the same as carbon
monoxide.
methane ……comes from cattle as they digest their food. The gas
also comes from fields where rice is grown in paddy fields.
nitrous oxide …when plants die and rot, nitrous oxide is pro-
duced.
ozone …..occurs naturally in the atmosphere.
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THE ENHANCED GREENHOUSE EFFECT…..
Some of the activities of man also produce greenhouse gases. These
gases keep increasing in the atmosphere. The balance of the green-
house gases changes and this has effects on the whole of
the planet.
Burning fossil fuels - coal, oil and natural gas - releases
carbon dioxide into the atmosphere. Cutting down and
burning trees also produces a lot of carbon dioxide.
A group of greenhouse gases called the chlorofluorocarbons, -
which are usually called CFCs, because the other word is much too
long!- have been used in aerosols, such as
hairspray cans, fridges and in making foam plastics. They are found
in small amounts in the atmosphere. They are dangerous greenhouse
gases because small amounts can trap large amounts of heat.
Because there are more and more greenhouse gases in the
atmosphere, more heat is trapped which makes the Earth
warmer. This is known as GLOBAL WARMING.
A lot of scientists agree that man's activities are making
the natural greenhouse effect stronger. If we carry on polluting the
atmosphere with greenhouse gases, it will have very dangerous
effects on the Earth.
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THE EFFECTS……
With more heat trapped on Earth, the planet will
become warmer, which means the weather all over
Earth will change. For example, summers will get hotter, and win-
ters too. This may seem a good idea, but the conditions we are liv-
ing in are perfect for life, and a large rise in temperature could be
terrible for us and for any other living thing on Earth. At the mo-
ment, it is difficult for scientists to say how big the changes will
be and where the worse effects will occur.
THE WEATHER….
In Britain, winter and summer temperatures will
increase and the weather will be warmer. In winter it may also rain
more but in summer it may become drier.
In other parts of the world, the effects will be different, some
places will become drier and others will be wetter. Although most
areas will be warmer, some areas will become cooler. There may be
many storms, floods and drought, but we do not know which areas
of the world will be affected.
All over the world, these
weather will affect
the kind of crop that can be
grown. Plants, animals and
even
people may find it difficult to
survive in different conditions
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SEA LEVELS…..
Higher temperatures will make the water of the
seas and oceans expand. Ice melting in the
Antarctic and Greenland will flow into the sea. All over the world,
sea levels may rise, perhaps by as much as 20 to 40 cm, by the be-
ginning of the next century.
Higher sea levels will threaten the low-lying
coastal areas of the world, such as the Nether-
lands and Bangladesh. Throughout the world, mil-
lions of people and areas of land will be at danger
from flooding. Many
people will have to leave their homes and large
areas of farmland will be ruined because of floods. In Britain, East
Anglia and the Thames estuary will be at risk from the rising sea.
FARMING…
The changes in the weather will affect the types of
crops grown in different parts of the world. Some
crops, such as wheat and rice grow better in higher
temperatures, but other plants, such as maize and
sugarcane do not. Changes in the amount of rainfall
will also affect how many plants grow.
The effect of a change in the weather on plant growth may lead to
some countries not having enough food. Brazil, parts of Africa,
south-east Asia and China will be affected the
most and many people could suffer from
hunger.
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WATER…..
Everywhere in the world, there is a big
demand or water and in many regions,
such as the Sahara in Africa, there is not enough water for the
people. Changes in the weather will bring more rain in some coun-
tries, but others will have less rain. In Britain, the Southeast will
be at risk from drought.
IN DANGER!
PLANTS & ANIMALS…
It has taken million of years for life to become used to the condi-
tions on Earth. As weather and temperature changes, the homes of
plants and animals will be affected all over the
world. For example, polar bears and seals, will
have to find new land for hunting and living, if
the ice in the Arctic melts.
Many animals and plants may not be able to
cope with these changes and could die. This could cause the loss
of some animal and plant species in certain areas of the world or
everywhere on Earth.
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PEOPLE…..
The changes in climate will affect
everyone, but some populations will be
at greater risk. For example, countries
whose coastal regions have a large population, such as Egypt and
China, may see whole populations move inland to avoid flood risk
areas. The effect on people will depend on how well we can adapt to
the changes and how much we can do to reduce climate change in
the world.
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THE WATER-CYCLE Understanding how the water cycle operates is key to understanding
how rivers work. The water cycle is also known as the hydrological
cycle. It is called a cycle because water continuously moves around
the system. Rivers are part of this cycle. The illustration below
shows how water changes state through the cycle. It can be a liq-
uid, a vapour or a solid.
How does the water cycle work?
• Energy from the Sun heats the surface of the Earth.
Water is evaporated from oceans, rivers, lakes, etc.
The warm, moist air rises because it is less dense.
Condensation occurs when water vapour is turned back into water droplets
as it cools down. Clouds are formed.
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CONT….
When the precipitation reaches the surface, some falls directly into
the sea but other water falls on land:
Some water is intercepted by vegetation. Some water may then
slowly reach the ground. Some will evaporate from the surface
of leaves or be taken up by the plant roots, and some of this
water will eventually return to the air as vapour through the
process of transpiration. This slows down or prevents some wa-
ter flowing back to the river.
Some water flows across the surface of the ground - surface run-
off. This happens when the surface doesn't allow water to penetrate.
Surface run-off is more likely to occur if the ground
is saturated with water or when the rock is impermeable. This water
moves quickly to the river.
Some water infiltrates into the soil. This through flow moves more
slowly back to the river than surface run-off.
Some water percolates deeper into the ground and is slowly trans-
ferred back to the river or sea.
Stores and transfers The major stores of water are the ocean, ice caps, land and the at-
mosphere. The movement of water between these stores is
called transfers.
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STALAGMITES AND STALACTITES
EROSIONAL LANDFORMS….
There is a lack of surface drainage in a limestone area. Much of the
water flows underground. The same chemical weathering process
happens below ground as above.
The weak carbonic acid in the water dissolves the limestone.
The running water carries it away in solution.
Over time, the water weathers away the rock along the joints and
bedding planes.
Caves, tunnels and larger caverns may form.
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DEPOSITIONAL LANDFORMS……
The water contains calcium carbonate in the water from the chemi-
cal weathering of limestone.
The water drips from the ceilings of the caves.
Some of the water evaporates, leaving behind some calcium car-
bonate.
The calcium carbonate forms ‘icicles’, producing stalactites, stalag-
mites and pillars.
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