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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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