The Restless Atmosphere
Weather
The Atmosphere
• The atmosphere is a blanket of gases surrounding the earth.
• It is made up of a mixture of different gases.
The Earth’s Atmosphere
The Earth’s Atmosphere
Solar Energy – Energy from the Sun
• The sun provides us with heat and light.
• However, not all of the sun’s energy reaches our planet.
– 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.
Latitude
• Latitude means distance
North or South of the
equator.
• It is measured in degrees.
• In general, the further a
place is away from the
equator, the colder it will
be.
• There are 3 reasons for
this.
Latitude
1. We know the sun’s energy is absorbed as it passes through the
atmosphere. Well, at the poles the atmosphere is thicker than at the
equator. Therefore, less heat gets through to the polar regions.
2. At the equator the sun shines directly overhead. This means the heat is
concentrated on a small area and so this area becomes hot.
3. At the poles the sun’s energy is slanted and it is spread over the curved
surface of the earth. This means it has to heat up a larger area and so this
area does not heat up as much.
In summary, less heat gets through to the poles. It has to heat up a large area.
Lots of heat gets through to the equator. It has to heat up a smaller area.
How Latitude influences Temperature
Wind
• Wind is moving air.
• Air moves from High pressure areas to Low Pressure areas.
Winds and Air Pressure
• Air moves from High Pressure areas to Low Pressure areas.
• Some places on the earth have high pressure and some have low
pressure. But why?
• Warm air rises leaving areas of low pressure.
• Cold air descends creating areas of high pressure.
High Pressure and Low
Pressure
Winds and Air Pressure
High and Low Pressure Areas
• If we apply this principle to the
earth we see that some places
on the earth’s surface will have
high pressure and other areas
will have low pressure.
• These areas of different
pressure create wind.
Global Wind Patterns
Global Wind Patterns
• We now know that winds
travel from HP areas to
LP areas.
• This creates a regular
pattern of the different
winds on the earth.
Global Winds and the Coriolis Effect
•
The earth is spinning on its axis.
•
Because of this the winds are
deflected at an angle.
•
They are deflected to the right in
the Northern hemisphere, and to
the left in the southern
hemisphere.
•
This is called the Coriolis Effect.
Ocean Currents
Air Masses
•
An air mass is a body of air with its own temperature, pressure, and
humidity level.
•
Air masses can effect the weather of the countries they pass over.
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Many different air masses meet over Ireland so our weather changes a lot.
There are 4 different air masses which effect Ireland’s weather.
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1. Polar Air Masses
2. Continental Air Masses
3. Tropical Air Masses
4. Maritime Air Masses
Fronts
•
When two air masses meet they do not mix very well because of their
different temperature, pressure and humidity.
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Where the two air masses meet is called a Front.
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We will look at two types of Fronts, a Cold Front and a Warm Front.
Cold Fronts
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A Cold Front occurs when cold air moves in towards warm air.
The cold air forces the light warm air to rise.
As the warm air rises it cools and condensation occurs.
Clouds are formed and this leads to heavy rainfall.
Warm Fronts
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A Warm Front develops when warm air moves in towards cold air.
The warm light air rises up over the cold air.
As it rises it cools and condensation occurs.
Clouds are formed and this leads to rainfall.
Depressions
•
A Depression is an
area of Low
Atmospheric Pressure.
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Depressions are also
known as Cyclones.
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Depression often pass
over Ireland.
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Depressions bring wet
and windy weather.
This is why we receive
lots of rain.
Anticyclones
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An anticyclone is an
area of high pressure.
•
Anticyclones bring
clear sunny weather.
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There are few clouds
and a gentle breeze.
The Water Cycle
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Water is a Renewable Resource.
When rain falls, the water is recycled and eventually goes back to
the clouds to fall as rain again.
This is called the water cycle.
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There are 4 stages in the Water Cycle.
1.
2.
3.
4.
Evaporation
Condensation
Precipitation
Run-Off
Clouds
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Clouds are made when water vapour condenses into tiny droplets.
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There are many different types of clouds.
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The most common types of clouds are;
1.
2.
3.
Cirrus Clouds
Cumulus Clouds
Stratus Clouds
Rainfall
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Precipitation means hail, rain, sleet or snow.
•
Rain is the most common type of precipitation.
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Rain occurs when warm air is forced to rise. As the warm air rises it
cools. Cold air cannot hold as much water vapour as warm air, so
condensation occurs. Clouds are formed and rain occurs.
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There are 3 different types of rain, because there are 3 different reasons
why warm air is forced to rise.
1.
2.
3.
Relief rainfall
Frontal (cyclonic) rainfall
Convectional rainfall
Relief Rainfall
•
Relief rainfall occurs when;
- Warm moist air moves in from the sea.
- It hits a mountain range at the coast and is forced to rise.
- It cools as it rises.
- Condensation occurs, clouds form and it starts to rain.
Frontal Rainfall
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Frontal rainfall occurs when;
– Warm and cold air masses meet at a Front
– The warm air mass moves up over the cold air mass.
– The warm air cools and condensation takes place.
– Stratus clouds form and rain occurs.
Convectional Rainfall
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Convectional rain occurs when;
– The sun shines on the land and heats up the air above it.
– The heated air rises quickly.
– As it rises it cools and condensation occurs.
– Cumulus clouds are formed and heavy rain occurs.
The Weather
•
When we talk about the weather we usually talk about the
following things.
1.
2.
3.
4.
5.
6.
7.
Temperature
Precipitation (rain etc)
Sunshine
Wind speed
Wind direction
Atmospheric pressure
Humidity
All of these different aspects of the weather can be measured.
There are different weather instruments to measure each thing.
These instruments are usually in a weather station.
Temperature
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Temperature is
measured using a
Thermometer.
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It is measured in
degrees Celsius (°C).
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Lines on a weather
map showing areas of
equal temperature are
called Isotherms.
Temperature
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You need to know how to calculate the;
1. Mean Temperature
2. Temperature Range
Mean Temperature: Add all the monthly temperatures, then divide by 12.
Temperature Range: Take the lowest temperature away from the highest temperature.
Mon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sept
Oct
Nov
Dec
Mean
Monthly
Temp
10
13
15
17
18
21
23
28
21
15
12
11
Precipitation
• Precipitation is
measured using a Rain
Gauge.
• It is measured in
millimetres.
• Lines on a map
showing areas of equal
precipitation are called
Isohyets.
Sunshine
• Sunshine is measured
using a Campbell
Stokes sunshine
recorder.
• Sunshine is measured
in Hours per day.
• Lines on a weather map
showing areas of equal
sunshine are called
Isohels.
Wind
• We can measure 3 things about the wind.
• Wind Speed – Using an Anemometer.
• Wind Direction – Using a Wind Vane.
• Wind Strength – Using the Beaufort Scale
The Beaufort Scale
• The Beaufort Scale
describes the effect
the wind has on the
landscape.
• Wind strength is
divided into 12 forces.
• The Beaufort Scale
was invented by an
Irishman.
Atmospheric Pressure
• Atmospheric pressure is
measured using a
Barometer.
• It is measured in
millibars.
• Lines on a weather map
showing areas of equal
pressure are called
Isobars.
A Barograph can also be used to measure atmospheric pressure
Humidity
• Humidity is measured
using a Hygrometer.
• A common type of
hygrometer is a wet and
dry bulb thermometer.
• It is expressed as a %.
100% is the maximum.
The Greenhouse Effect
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The Greenhouse Effect
occurs naturally.
•
When the sun shines it
heats up the earth.
•
Some of the heat gets
trapped in gases in the
atmosphere.
•
It is a positive thing
because without the
Greenhouse effect the
earth would be too cold for
us to live on.
Global Warming
•
Carbon dioxide and
methane are Greenhouse
gases in the atmosphere.
•
The amount of these gases
has increased a lot in
recent years.
•
Therefore, more of the
sun’s heat is being trapped
in the atmosphere.
•
This is making the earth
warmer. This is called
Global Warming.
The Greenhouse Effect and Global Warming
Causes of Global Warming
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There are a number of reasons why Global Warming is taking place.
1.
There is a big increase in the amount of Carbon dioxide in the atmosphere.
2.
People are burning more fossil fuels, oil, coal, gas.
3.
Tropical rainforests are being cut down. Trees absorb C02 and so less trees
means more C02 in the atmosphere.
4.
There are more CFC’s in the atmosphere. These are bad gases which trap
lots of the sun’s heat.
The Effects of Global Warming
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Global warming will create many problems for people in the near
future. These include;
1.
2.
3.
The Polar ice caps will melt causing sea level to rise.
Low lying countries or regions may be flooded.
Some parts of the world will become drier. It will be more difficult
for farmers to grow crops.
This may lead to drought and desertification.
4.
However, it may also bring some positive things. Some countries that
are now cold may become warmer, allowing more crops to be grown.
Solutions to Global Warming
•
If we want to stop the problem of global warming there are a
number of things we need to do. These include;
1.
2.
Stop using fossil fuels such as coal and oil.
Use more renewable energy sources such as wind, wave and
solar power.
Reduce Deforestation - Plant more forests and stop cutting down
the forests we have.
Encourage energy conservation - Save energy at home by using
less electric items and walk / cycle instead of using cars or buses.
3.
4.
Revision Questions
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Name 3 gases in the atmosphere.
Why does all of the energy from the sun not reach planet earth?
What does Latitude mean?
How does Latitude influence the temperature of a place?
What is wind and why does it occur?
What is the Coriolis Effect?
Name two Cold Ocean Currents and two Warm Ocean Currents.
List 4 air masses that effect Ireland’s weather?
What effect do each of these air masses have on Ireland’s weather?
Explain with diagrams the difference between a Cold and a Warm Front.
What is a Depression and what type of weather does it bring?
What is an Anticyclone and what type of weather does it bring?
Draw and label a diagram of The Water Cycle.
Revision Questions
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List 3 types of clouds.
List 3 types of rainfall and use diagrams to show how they are different.
List 7 things you can measure about the weather and draw the instrument
used to measure each thing.
What is the Greenhouse Effect and why is it happening?
What is Global Warming and why is it happening?
What effects is Global Warming having on our planet?
What can we do to solve the problem of Global Warming?