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THE RESTLESS
ATMOSPHERE
The Atmosphere
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The atmosphere is a blanket of gases surrounding
the earth.
It is made up of a mixture of different gases:
Nitrogen – 78%
Oxygen – 21%
Others – 1%
It is important because it provides us with the air we
breathe, absorbs heat from the sun by day, retains
heat at night and protects us from harmful rays from
the sun.
The Atmosphere
Troposphere
The troposphere is the
bottom layer of the
atmosphere.
12km thick, 75% of the
earth’s gasses are found in
this layer.
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The Heat Machine
The sun is a huge mass of burning
gases that give off s0lar energy.
 50% of the sun’s energy reaches
planet earth.
 25% is deflected back into space by
dust and clouds in the atmosphere.
 25% is absorbed as it passes through
the atmosphere.
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The Heat Machine
Uneven Heating of Earth
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The surface of Earth is unevenly heated by the
incoming solar energy. The amount received at any
place on Earth’s surface depends on the latitude of
that place and tilt of Earth’s axis.
At the poles, less heat gets through.
At the equator, the sun shines directly overhead.
At the poles, the sun’s energy is slanted.
Winds and Air Pressure: Atmosphere
On the Move
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The troposphere is always in motion. This moving air is
called wind.
Winds form because the sun heats different parts of
Earth unequally.
When air is heated, it expands and becomes lighter. It
rises and creates an area of low atmospheric pressure.
When air is cooled, it becomes heavier and descends. It
presses down on Earth’s surface and creates an area of
high atmospheric pressure.
Air moves from high pressure areas to low pressure
areas.
Seasons and the Sun
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Earth orbits the sun once every 365¼ days. During this orbit,
different parts of earth are tilted towards the sun at
different times of the year. These parts receive more direct
sunlight than those that are tiled away from the sun.
In the Summer in the northern hemisphere:
The sun is tilted towards it.
Days are long while nights are short.
It receives much more solar energy, so its weather is
warmer.
In the Winter in the northern hemisphere:
The sun tilted away from it.
Days are short while nights are long.
It receives much less solar energy, so its weather is colder.
Winds and Air Pressure: Atmosphere
On the Move
Types of Winds
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Winds are named after the direction from which
they blow.
The wind that is most frequent in an area is called
the prevailing wind.
Winds that blow from the equator towards the poles
are warm winds.
Winds that blow from the poles towards the equator
are cold winds.
Global Wind Patterns
Ireland’s Synoptic Stations’ Prevailing
Winds
Coriolis Effect
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The coriolis effect is the earth spinning on its axis.
This is because of the winds being deflected at an
angle.
They are deflected to the right in the northern
hemisphere and the left in the southern hemisphere.
Doldrums are areas close to the equator where the
wind speeds are very low or where they have died
out entirely.
Trade winds were named as a result of their ability
to quickly drive trading ships across the ocean.
Coriolis Effect
Ocean Currents
The heating of the oceans
is very unequal due to
different latitudes.
Therefore, there are
different ocean currents.
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Ocean Currents
Air Masses and Weather Systems
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Air masses are large bodies of air that have similar
temperature, pressure and moisture throughout.
There are 4 types of air masses on Earth and they
are:
Maritime air masses which tend to bring rain.
Continental air masses which tend to be dry.
Polar air masses which bring cold air.
Tropical air masses which bring warm air.
Air Masses
Fronts
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A front is a boundary area where two different air
masses meet.
Cold Front
A cold front occurs when a cold air mass
pushes in and replaces a warm air mass.
Warm air mass is lighter so it is forced to
rise rapidly into the atmosphere.
 As the warm air rises, it cools and
condensation takes place. Masses of cloud
develop. Heavy rain falls along the front.
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Cold Front
Warm Front
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A warm front occurs when a warm air mass
approaches a cold air mass. The warm air is lighter
so it rises up over the cold air.
As the warm air rises, it cools and condenses to form
dark, rain-bearing clouds. Continuous rain soon
follows.
Thunderstorms are normally associated with these,
especially in the Summer.
Warm Front
Stationary Front
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A stationary front forms when a cold front or
warm front stops moving. This happens when two
masses of air are pushing against each other but
neither is powerful enough to move the other.
Winds blowing parallel to the front instead of
perpendicular can help it stay in place.
It normally is associated with heavy rain and
temperatures in the low-mid teens whether it is a
Winter or Summer month.
Stationary Front
Occluded Front
At an occluded front, the cold air
mass from the cold front meets the
cool air that was ahead of the
warm front. The warm air rises as
these air masses come together.
 Occluded fronts usually form around
areas of low atmospheric pressure
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Occluded Front
Depressions
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A depression is an area of low pressure and is associated with unsettle
weather, including rain, cloud and wind.
In the case of Atlantic depressions, warm, moist tropical air from the south
meets colder, drier polar air from the north.
Due to these differences, the air masses do not mix easily. The warm air is
lighter and is forced to rise, creating an area of low pressure at ground
level.
At the same time, the air begins to move in an anticlockwise direction in the
north hemisphere. The cold front begins to wrap itself around the back of
the warm air. The warm air is now trapped in a warm sector.
The cold front travels faster than the warm front and gradually begins to
catch up with it. Eventually, it lifts the warm air completely off the ground.
The ground air now consists entirely of cold air and the depression is over.
Ireland’s weather is dominated by Atlantic depressions that pass over the
country for much of the year.
They are also known as cyclones.
Depressions
Anticyclones
An anticyclone is an air mass
with high pressure at the centre.
In the Summer, they bring hot,
sunny weather.
In the Winter, they bring cold,
sunny weather.
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Anticyclones
The Water Cycle
Clouds
Type of Cloud
Appearance
Location
Fact
Weather
Cirrus
Wispy like a
lock of hair
High altitude
Made of ice
crystals
Fair, dry and
sunny
Cumulus
Fluffy or woolly
and pitch black
Medium altitude Known as fair
weather
clouds
Thunderstorms,
heavy rain
Stratus
Puffy and grey
Low altitude
Drizzle, light rain
If they reach
ground level,
they are
called fog
Precipitation: Types
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When cloud particles become too heavy to remain
suspended in the air, they fall to the earth as
precipitation. Precipitation can be anything falling
from the clouds, including rain, snow, hail and sleet.
Rainfall is the most common form and there are
three types:
Relief rainfall
Cyclonic (frontal) rainfall
Convectional rainfall
Relief Rainfall
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A warm wind evaporates water from the sea and
blows it to the land.
The air is forced to rise when it reaches high ground.
As it rises, it cools.
Condensation forms cloud because the cooled air
can’t hold as much moisture.
The droplets then join and get heavier. Rain then
falls on the windward slope.
On the leeward slope, the air descends and gets
warmer. The cloud evaporates so there is very little
rain.
Relief Rainfall
Cyclonic (Frontal) Rainfall
A warm wind blows towards the cold air.
 When the warm air reaches the cold air, it
rises because it is lighter. As it rises, it
cools.
 Condensation takes place and clouds form
(stratus clouds) because the cold air
cannot hold as much moisture.
 The droplets join and get heavier, so rain
falls.
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Cyclonic (Frontal) Rainfall
Convectional Rainfall
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The sun heats the ground all morning. The air near
the ground gets warm and moisture is evaporated.
By early afternoon, the heated air expands, it
becomes lighter and rises. The rising air then cools.
Condensation takes place and clouds form (cumulus
clouds). The cool air is unable to hold all moisture.
The droplets then join together and gets heavier and
rain falls.
Convectional Rainfall
Weather
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Weather is the word used to describe the state of
the atmosphere at any particular time and place.
The study of weather is called meteorology.
Meteorologists prepare weather forecasts.
Ireland is a country of many different types of
weather but rainfall is very common and it rains for
more than half the year in Ireland.
Met Éireann of Glasnevin is the headquarters of
weather forecasting in Ireland.
The thermometers and barograph is placed inside
a Stevenson screen.
Importance of Weather Forecasts
The upcoming weather will influence
what we wear and the activities that
we undertake.
 It may affect our mood.
 Some occupations require very
accurate weather forecasts such as
farming, fishing, tourism, air traffic
and sport.
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Weather
Element
Instrument
Unit of Measurement
Isoline Maps
Temperature
Dry bulb thermometer
°C/Degrees Celsius
°F/Degrees Fahrenheit
Isotherms
Maximum thermometer
Minimum thermometer
Humidity
Hygrometer
Percentages (%)
Precipitation
Rain gauge
Millimetres (mm)
Isohyets
Sunshine
Campbell-Stokes recorder
Hours (hrs)
Isohels
Wind Speed
Anemometer
(Beaufort scale)
Km/hr or mph or knots
Isotachs
Wind Direction
Wind vane
Directions
Air Pressure
Aneroid barometer
Millibars
(mb)/Hectopascals (hPa)
Isobars
Temperature
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Temperature tells us how hot or cold it is in an area.
It is measured in ºC/ºF.
It is measured using a thermometer.
Celsius is also known as centigrade.
The liquid in a thermometer is known as mercury.
Isotherms are lines on a weather map that join places
of equal temperature.
Mean temperature = Sum of temperatures ÷ number of
months/days
Temperature range = Maximum temperature −
Minimum temperature
Thermometer
Humidity
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Humidity is the amount of water vapour in the air.
It is measured in %.
It is measured with a hygrometer.
The difference in temperature between the two
thermometers is used to find the relative humidity.
The greater the difference between the
temperatures, the lower the relative humidity.
Hygrometer
Precipitation
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Precipitation is any form of moisture falling from
clouds. Mainly in the form of rain, snow and hail.
Rainfall is measured in millimetres (mm).
Snowfall is measured in centimetres or inches
(cm/ins).
It is measured using a rain gauge.
Isohyets are lines on a weather map that join places
of equal precipitation.
Rain Gauge
Sunshine
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Sunshine is the shining of the sun.
It is measured in hours (hrs).
It is measured by a Campbell-stokes sunshine
recorder.
Isohels are lines on a weather map that join places with
equal amounts of sunshine.
The glass sphere concentrates the rays of the sun onto a
spot on strip of paper.
The paper is marked off in hourly intervals.
If the sun is shining, it burns a mark on the paper. If the
sun does not shine, the paper is unmarked.
As the sun moves across the sky, its rays concentrate on a
different section of paper.
Campbell-Stokes Sunshine Recorder
Wind Speed
The wind speed tells us how strong
the wind is.
 It is measured using an anemometer.
 It is measured in either km/hr or mph.
 Isotachs are lines on a weather map
that join places with equal wind
speed.
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Anemometer
Wind Direction
The direction of the wind is
indicated by a weather
vane.
Wind direction is described
by the direction from which
the wind is blowing.
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Wind Vane
Air Pressure
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The air pressure tells us the weather we expect in a
region. The lower it is from 1000hPa, the wetter or
stormier it is. The higher it is from 1000hPa, the drier
or sunnier it is.
It is measured using a barometer or aneroid
barometer.
A barograph connects a barometer to a chart to
record the air pressure.
It is measured in either hectopascals (hPa) or
millibars (mb).
Isobars are lines on a weather map that join places
of equal pressure.
Barometer
El Niño
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El Niño is a weather pattern that leads to different weather
conditions around the world with most affects on the Pacific Ocean.
It happens every 2-7 years.
The Pacific waters warm up by at least 1 degree above normal.
Fewer Atlantic hurricanes take place but areas around the Gulf of
Mexico are still expected to be wetter than normal.
Drier than normal conditions are expected in the Ohio Valley region
as well as the northwest of the USA.
It gives away to wetter than normal conditions in South America.
The monsoon season in Asia is weaker than normal.
More active typhoons take place in the Pacific Ocean due to the
warm waters.
Some evidence show it gives very cold Winters to north, east and
west Europe.
The Greenhouse Effect and Global
Warming
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The greenhouse effect is when gases of the
atmosphere trap much energy into it and they act
like the glass on a greenhouse because they let heat
in and prevent most of it getting out.
Carbon dioxide, methane, chlorofluorocarbons
(CFCs) and nitrous oxide are the most effective
gases at trapping heat.
Due to the atmosphere trapping gases like a
greenhouse, global warming takes place.
Earth is over 6x warmer than it was in 1900.
Causes of Global Warming
Cause
Description
Burning of fossil fuels
Burning fossil fuels in homes, factories and power
stations raises the level of carbon dioxide in the
atmosphere.
Deforestation
Trees absorb carbon dioxide and give off oxygen in its
place. As more forests are cut down, there are fewer
trees to perform this function.
Methane
Cattle produce methane as they digest their food.
Methane is also released into the atmosphere from
decaying organic matter in landfill sites.
Burning of fuels
The use of nitrates as a fertiliser also adds to the
increase of the gas in the atmosphere.
CFCs
The use of cfs in fridges, aerosols and foams has been
reduced because they damage the ozone layer. They
are the most damaging greenhouse gas.
Impacts of Global Warming on the
World
Impact
Description
A rise in sea levels
As global temperatures increase, the polar
ice caps will melt. Sea temperatures will
increase and the water in them will
expand. Overall, sea levels will rise by up
to 60 cm over the next century.
Climate change
Tropical storms and hurricanes will become
more frequent and stronger. The hurricane
season may also become longer. Rainfall
patterns will change and weather
forecasting will become unpredictable.
Impacts of Global Warming on Ireland
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1. Ireland's soft rains will become strong downpours in the north and
west and will lead to increased flooding & bogbursts.
2. Summers in the south and the interior will become warmer and
drier. This may lead to water shortages. It will also lead to a change
in agriculture as crops replace grass. This will impact on livestock
farming.
3. If the North Atlantic Drift slows down, it will have less of a
warming effect on our shores.
4. Low lying areas will be open to flooding from both rising sea
levels and increased storm strength and frequency. Soft coastlines
will be open to erosion. Land will be lost as sea defences are too
expensive.
5. While drier summers will have a negative impact on growing crops
such as potatoes, Mediterranean crops may be grown instead.
6. Storm activity will become more frequent and more severe.
Solutions to Global Warming
Solution
Description
Clean energy
Reduce dependence on fossil fuels. Use cleaner and
renewable energy sources such as solar, wind, wave
and hydropower.
Reduce deforestation
This should be accompanied by reafforestation
(replanting trees), especially in tropical regions.
Reduce, reuse and recycle
Reduce the need for manufactured goods and their
transport over long distances.
Use energy-efficient appliances
These include lights, fridges and heaters.