UNIT 5. THE ATMOSPHERE

Designed by Conchi 1B1

1. THE ATMOSPHERE

� The atmosphere is a thin layer of gases that

surrounds the Earth.

� The atmosphere is made up of air.

� Air: It is a mixture of gases that forms the atmosphere. It

is composed of nitrogen (78%), oxygen (21%), carbon

dioxide (0.03%) and very small amounts of other gases

(helium, argon, neon, ozone, water vapor, etc.).

� In the atmosphere there is also: powder, bacteria, pollen,

etc.

1. THE ATMOSPHERE

� The primitive atmosphere: the atmosphere was

very difference 4600 millon years ago.

• Was made up of:

- Water vapour

- Carbon dioxide

- Hydrogen

- Ammonia

- Methane

- Other oxides

• The first living beings (bacteria),

produced oxygen by photosynthesis.

• Molecules formed when chemical

reactions took place between gases.

These molecules fell to Earth with rain.

1. THE ATMOSPHERE

� Importance of the atmosphere:

� In the first place, the atmosphere contains oxygen which is

necessary for living beings. We all need air to breathe.

� Secondly, the temperature of the Earth depends on the atmosphere. The atmosphere favours the warming of the Earth. It absorbs a great part of solar radiation and prevents this from escaping back up into space. This is called the greenhouse effect. Without the atmosphere our planet would be much colder.

� Finally, the atmosphere is a very important filter. There is a layer of a gas called ozone which protects us from some dangerous radiation.

2. THE LAYERS OF THE ATMOSPHERE

� The layers of the atmosphere are:

� Troposphere: It is the lowest layer of the Earth's atmosphere. It extends from 0 to 12 km of altitude (very thin), but contains 80% of the total mass of the atmosphere. The temperature decrease with the altitude. The weather, clouds, wind, rain, etc. occur in the troposphere.

� Stratosphere: extends from 12 km to 50 km. There is an increase of temperature with the altitude. The ozone layer is in the middle.

� Mesosphere: extends from 50 km to 80 km. Here the temperature is very low. It contains clouds of ice and dust. The meteorites that fall to the Earth become incandescent in this layer (shooting stars)

� Thermosphere or ionosphere: extends from 80 km to 500 km. In this layer there are very few gases. The temperature increase a lot due to X-rays and gamma rays from Sun. Auroras occur in the ionosphere. Comets appear here.

� Exosphere: begins at 500 km of altitude and it isn’t really clear where it ends. It is the outermost layer of the Earth's atmosphere. The atmospheric pressure and temperature are low.

2. THE LAYERS OF THE ATMOSPHERE

� The layers of the atmosphere are:

12 km

50 km

80 km

500 km

3. THE WEATHER

� The weather describes the state of atmospheric conditions at a certain place, over a short period

of time.

� Weather conditions include:

� Humidity: The concentration of water vapour in the atmosphere.

� Clouds: Formed when rising air cools.

� How are the clouds formed?: In the areas heated by the Sun, the water evaporates and goes up to the

troposphere. In the high part of the troposphere, the water vapour cools down. The cold vapor is

condensed in small drops. Those drops form the clouds. There are three basic types of clouds: cirrus,

cumulus and stratrus.

� Precipitation: Water that falls to the ground. They can be of several types.

� Rain: The small drops join in the cloud, they weigh too much and they fall in the form of rain.

� Snow: Snowflakes form in clouds where the temperature is freezing (0ºC). The ice crystals (flake) form

around tiny bits of powder that have been carried up into the atmosphere by the wind. As the snow

crystals grow, they become heavier and fall toward Earth.

� Hail: The drops join, but instead of falling in the form of rain, the wind blows them up to high and cold

areas, they freeze and they form balls of ice that fall on the Earth.

� Temperature: How hot or cold the air is.

� Wind: Is the air moving.

� How is the wind formed?: Hot air weighs less and goes up, the cold air of the high layers, comes and

occupies the place that the hot air left free. The wind is that current of air.

3. THE WEATHER

3. THE WEATHER

� ATMOSPHERIC PRESSURE:

� Air has weight.

� The pressure it exerts on the

surface is called atmospheric

pressure.

� It is caused by gravity

� It is measured in millibars (mb)

o High pressure area or anticyclones (H or A):

are stable situations and the weather is good.

When there is an anticyclone the weather is

sunny

� PREDICTING THE WEATHER:

o Low pressure area or cyclones (L or B):

are unstable atmospheric situation.

When there is a cyclone over a particular

place the weather is usually very bad, it’s

windy and it rains or snows.

4. THE METEOROLOGY

� The meteorology is the study of different atmospheric variables to make weather

predictions.

� Meteorologists collect information about temperature, precipitation, wind, the humidity of the air,

atmospheric pressure and clouds.

� Meteorological instruments:

� A thermometer: is a device that measures the temperature. Temperatures are expressed in

centigrade grades (ºC) and in some countries in Fahrenheit grades (ºF).

� A pluviometer (rain gauge): is a type of instrument that picks up and measures the quantity of

fallen rain. Unit: litre per square metre.

� A barometer: is an instrument used to measure atmospheric pressure. Unit: mb

� An anemometer: is a device to measure wind speed. Unit: m/s or Km/h

� A hygrometer: is an instrument used for measuring humidity. Atmospheric humidity is

expressed as a percentage

� A vane: is a movable device attached to an elevated object such as a roof for showing the

direction of the wind.

4. THE METEOROLOGY

5. ATMOSPHERIC POLLUTION

� What is the atmospheric contamination?: It is the presence of a certain amount of

substances in the atmosphere that can damage or endanger the health of people and

of living creatures.

� What contaminates the atmosphere?: The atmosphere can be contaminated in several

ways:

� By polluting substances as noxious gases or particles of smoke and ashes.

� By noises and light.

� Effects of contamination:

� The climate suffers from changes.

� The biosphere is seriously harmed.

� The health of people worsens.

� Constructions and materials deteriorate more quickly.

5.1 POLLUTION IN CITIES

� All cities are a source of pollution for the atmosphere.

� Common air pollutants are carbon monoxide, carbon dioxide, sulfur dioxide

and nitrogen oxides.

� They come from industries, homes and motor vehicles.

� The contaminating substances can cause respiratory diseases and lack of

visibility. This problem is called smog (smoke + fog = smog).

5.2 GLOBAL WARMING

� The average temperature of the planet is increasing since the mid-twentieth

century. This phenomenon is called global warming and it’s a result of the

increase in the greenhouse effect.

� The greenhouse effect is a natural phenomenon and it is essential for keeping

the Earth warm enough for living beings. But, some polluting gases, as carbon

dioxide (CO2), increase this effect too much.

� Carbon dioxide is released by the burning of coal and oil in our cars and power

stations. Besides, the deforestation also increases the CO2 levels.

� Global warming has many harmful consequences: temperatures rise, ice at the

North and South Poles melts, sea level rises and many coastal cities may be

flooded.

� We should save energy, stop using oil, gas and petrol and we should change to

green energy (wind power, solar power, hydroelectricity...) and, of course,

stop cutting down trees

https://www.youtube.com/watch?v=aFsC4sGzMJ8

5.3 THE HOLE IN THE OZONE LAYER

� Ozone (O3) is a triatomic molecule, consisting of three oxygen atoms. Ozone in

the stratosphere filters ultraviolet light from reaching the Earth's surface.

� There is an area where the ozone layer is disappearing. This area is called the

hole in the ozone layer.

� Due to the hole in the ozone layer, harmful radiation affects our health causing

skin diseases.

� The disappearance of ozone is caused by some gases called CFC. These gases

were in refrigerators and aerosols but today they are substituted by other

gases which do not damage the ozone layer.

https://www.youtube.com/watch?v=u9ztDSbSrFI

5.4 ACID RAIN

� Acid rain is a rain or any other form of precipitation that is unusually acidic.

� Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which

react with the water molecules in the atmosphere to produce acids.

� Acid rain produces adverse impacts on forests, freshwaters and soils. Besides

it is harmful to insect and aquatic life-forms, as well as causing damage to

buildings and having impacts on human health.

6. PROTECTING THE ATMOSPHERE

� When pollution is reduced, global warming, the hole in the ozone layer and

acid rain are also reduced.

� By saving energy, the atmosphere will improve and our health will be much

better.

� You are part of the solution.

� Use hot water carefully: do not wate it

� Turn off unneccessary heating and electrical devices

� Travel by public transport, by bike or on foot

� Avoit aerosols with CFCs

� Recycle paper, plastic and glass

� Plant trees.