Download CE Weather Wind and Pressure

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Y6 Weather III
Brambletye Geography Department
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Contents:
NOTE: This booklet should be kept for revision notes for Year 7 and Year 8.
Traffic
Light
Section
1.
2.
3.
4.
5.
6.
7.
8.
A
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Wind: an ‘element’ of the weather
The Beaufort Scale
The Atmosphere
Why does the wind blow?
Where does our weather come from?
Anticyclones
Depressions (page 1)
Depressions (page 2)
What do my marks mean?
Key to traffic lights:
I do not understand this
I understand most of this
I understand this really well
Accuracy:
How well have you completed the task?
0 = not done; 5=excellent
Effort:
A= 5
E= 5
Have you tried your best?
0 = no!; 5=excellent work
The topic that I enjoyed the most was …………………………………………………………………………………….
The topic that I found the easiest was ……………………………………………………………………………………
The topic that I found the hardest was …………………………………………………………………………………..
Please complete this page at the end of the term.
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Y6 Weather III
Brambletye Geography Department
1. Wind: an ‘element’ of the weather
Wind is one of the ‘elements’ of the weather. It is not an element in scientific terms, but
one of the phenomena in the atmosphere that we can observe and measure.
“Weather is ________________________________________________
_________________________________________________________”
Warning: Do not confuse weather and climate!
“Climate is the general type of weather that an area experiences”
Note:
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Climate is normally calculated on a 30 year average
Climate normally focuses on rainfall and temperature and how they change month by
month
“Wind is ___________________________________________
_________________________________________________________”
There are two features of wind that we can
measure: the direction that it is moving in and the
speed that it is travelling in.
The photograph on the right shows the equipment
that is used to measure wind on a weather station.
The arrow on the left points the direction that the
wind is coming from.
The speed that the cups rotate, tell us how fast the
wind is blowing.
Wind speed is measured in …………………………… using a ……………………………………
Wind direction is measured in ……………………….. using a …………………………………….
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Y6 Weather III
Brambletye Geography Department
2. The Beaufort Scale
The Beaufort Scale
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If you do not have an anemometer, then wind
speed can be measured by looking at the way
that the wind affects the world around you.
What is the difference between a ‘gentle breeze’
and a ‘light breeze’?
In 1805, Francis Beaufort, an officer in the Irish
Navy suggested a scale that could be used to
measure wind speed without expensive
equipment and, more importantly he
standardised the words that were used to
describe wind.
His scale ran from 0 (no wind at all), to 12, a
devastating hurricane.
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Y6 Weather III
Brambletye Geography Department
My Beaufort Scale
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 On the grid, below design your own Beaufort Scale and draw a diagram to show what happens
in each step.
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Y6 Weather III
Brambletye Geography Department
3. The Atmosphere
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The layer of gases that surrounds the Earth and separates the surface from the void of
space is known as the atmosphere.
The atmosphere is held in place by gravity.
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The Earth's atmosphere contains a mixture of gases is commonly known as air:
o 78% nitrogen
o 21% oxygen
o 0.93% argon
o 0.04% carbon dioxide - although this is increasing
o water vapour (average of 1% - but that varies)
o trace amounts of other gases.
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The atmosphere is densest at the surface and it gets ‘thinner’ as you go up towards space.
Due to the spinning action of the Earth, the atmosphere is deeper at the equator and
shallower at the poles.
There are a series of layers or ‘spheres’ that you would pass through if you travelled up
through the atmosphere:
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The layers of the atmosphere
EXOSPHERE
Thermopause
80km
Mesopause
Stratopause
Tropopause
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Y6 Weather III
Brambletye Geography Department
The troposphere:
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The troposphere is the layer closest to the Earth's surface, extending up to about 10-15
km above the Earth's surface.
It contains 75% of the atmosphere's mass.
Temperature and pressure drops as you go higher up the troposphere.
This is the layer where all of the weather happens.
The tropopause:
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At the very top of the troposphere is the tropopause where the temperature reaches a
(stable) minimum.
Some scientists call the tropopause a "cold trap" because this is a point where rising water
vapour cannot go higher because it changes into ice and is trapped.
If there is no cold trap, Earth would lose all its water!
The Greenhouse Effect:
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Heat from the Sun warms the Earth's surface but most of it is
radiated and sent back into space.
‘Greenhouse gasses’ such as water vapour and carbon
dioxide in the troposphere trap some of this heat, preventing
it from escaping thus keep the Earth warm. This trapping of
heat is called the "greenhouse effect".
If it was not for the greenhouse effect, our planet would be a
ball of ice and there would be no life on the planet.
However, if there is too much carbon dioxide in the troposphere then it will trap too much
heat. Scientists are afraid that the increasing amounts of carbon dioxide would raise the
Earth's surface temperature, bringing significant changes to worldwide weather patterns ...
shifting in climatic zones and the melting of the polar ice caps, which could raise the level
of the world's oceans.
This ‘enhanced’ greenhouse effect leads to Global Warming and climate change.
The Ozone Layer:
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The stratosphere contains a
thin layer of ozone which absorbs
most of the harmful ultraviolet
radiation from the Sun.
The ozone layer is being
depleted, and is getting thinner
over Europe, Asia, North
American and Antarctica : "holes"
are appearing in the ozone layer.
These holes are created by
pollution: especially the use of
CFCs in aerosol cans.
NOTE: The thinning of the ozone layer does not cause Global Warming!
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Y6 Weather III
Brambletye Geography Department
 Questions:
1. What is the atmosphere?
…………………………………………………………………………….
2. What is the most common gas found in the atmosphere? ……………………………………
3. What percentage of the atmosphere is oxygen ? ………………………………………………….
4. Where is the atmosphere deepest? …………………………………………………………………….
5. In which atmospheric layer does all of the weather occur? …………………………………….
6. In which atmospheric layer do satellites orbit the Earth? ………………………………………
7. Why is the tropopause important for the weather? ……………………………………………….
8. Why is the ‘greenhouse effect’ important? ……..…………………………………………………….
………………………………………………………………………………………………………..……………….
9. How is the ‘greenhouse effect’ being enhanced? …………………………………………………..
………………………………………………………………………………………………………..……………….
10. What will the effects of this ‘enhanced greenhouse effect’ be? ……………………………….
………………………………………………………………………………………………………..……………….
………………………………………………………………………………………………………..……………….
11. Why might holes in the ozone layer be considered a bad thing? ……………………..…….
………………………………………………………………………………………………………..……………….
12. How could the effects of global warming and climate change be reduced …
a. By industries and governments? ………………………………………………………………..
……………………………………………………………………………………………………………….
b. By you and your family? ………….………………………………………………………………..
……………………………………………………………………………………………………………….
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Y6 Weather III
Brambletye Geography Department
4. Why does wind blow?
Air pressure and wind:
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Air has mass.
The ‘weight’ of air above your head is the equivalent of an elephant!
When the air above us is rising then there is less pressure pushing down on us: this is
known as LOW pressure
When the air above us is sinking then there is more pressure pushing down on us: this is
known as HIGH pressure.
Air pressure is measured in …………………………… using a ……………………………………
Rising air
Sinking air
Ground
 Add the words ‘HIGH’ and ‘LOW’ to the diagram above.
 Draw and label arrows to show the direction that you expect wind to blow.
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When air is warmed, it becomes lighter and rises: this is felt as low pressure on the
ground.
When air is cooled, it becomes denser and sinks: this is felt as high pressure on the
ground.
Low pressure is generally associated with windy and unsettled weather.
High pressure is generally associated with stable weather (hot clear skies in the summer
and frosty mornings in winter)
Air in the atmosphere always seeks to be at equilibrium (the same temperature and
pressure, throughout).
Air will always move from an area of HIGH pressure to an area of LOW pressure. The
bigger the difference in pressure, the faster the air will move: the quicker the wind.
Consequently, watch the school weather station: whenever the air pressure gets below
990mb, you will notice that the wind starts to pick up. When it it gets to around 950mb, it
will be very windy indeed!
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Y6 Weather III
Brambletye Geography Department
Global winds:
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There are a series of global air circulations. These air movements are all started by strong
heating from the sun on the equator.
 Draw the global atmospheric convection currents
These circulations cause
the prevailing winds such
as the North Atlantic
Drift and the trade
North Pole
winds.
Tropic of Cancer
Equator
Tropic of Capricorn
Local winds:
South Pole
Local winds:
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Where there are differences in land cover, there will be differences in heating and winds
will be formed.
An example of this is onshore and offshore breezes that occur on the coast:
 describe how coastal winds change during the day.
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Y6 Weather III
Brambletye Geography Department
5. Where does our weather come from?
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Our weather in the British Isles is controlled by a series of huge ‘lumps’ of air known as air
masses.
These are generally high pressure areas with stable conditions.
o The air in these areas take on the regional climate characteristics (mainly in terms
of temperature)
o As the air travels towards the British Isles it picks up characteristics from the route
that it takes (mainly moisture if it travels across an ocean)
The spinning of the Earth and National weather conditions suck air across the British Isles
from the following places:
Air Masses affecting the British Isles
Activity:
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 Complete the table below and then put the correct abbreviations (Abbr.) into the correct circles
on the map above.
 If the air mass is warm, colour the arrow red; if it is cool, colour the arrow blue.
bbr.
Name
Location
Characteristics
Summer or Winter?
TM
Tropical
Maritime
South
Atlantic
Warm and
moist
All year around
PM
P
Labrador Sea
Polar
PC
Mainly Winter
TC
Hot and dry
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Mainly Summer
Y6 Weather III
Brambletye Geography Department
6. Anticyclones
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Anticyclones are areas of high pressure (over 1 bar or 1,000mb – or one atmospere’s
worth of air pushing down)
Air is sinking in an anticyclone and so they are normally very stable with little wind.
They are large weather systems and they move very slowly.
Wind travels around an anticyclone in a clockwise direction.
Weather forecast for midday Wednesday, 12th May.
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Y6 Weather III
Brambletye Geography Department
7. Depressions
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Depressions are areas of low pressure (under 1,000mb)
They are called depressions because the barometer dips when they are overhead.
Air is rising in a depression, spiraling anticlockwise and as a result they are unstable
systems with high winds, cloudy skies and rainfall.
They are quite fast-moving systems and they become stable quite quickly.
They occur where warmer air and cooler air meet: fronts.
Weather forecast for
midday Tuesday 24th April.
a.
b.
c. Air Masses
2. How does the weather come to the UK?
a. Depressions
b. Anticyclones
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Y6 Weather III
Brambletye Geography Department
Cross-section through a depression:
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Depressions move across the British Isles regularly and they bring with them a fairly
predictable pattern of weather.
Meteorologists use synoptic charts or weather maps to help them to plot the movement
of weather systems.
Synoptic charts have isobars on them: lines which join points of equal pressure.
The tighter the isobars are together, the faster the wind will be!
Synoptic chart and satellite image of
the lowest pressure ever recorded.
 On a synoptic chart, a depression appears as
‘sharks fin’ shape.
 The warm front is the leading edge of the
warm air.
 The cold front is the leading edge of the cooler
air.
 The cold front moves fast and lifts the warm air
off the ground (known as an occlusion)
 The whole system moves across the UK from
west to East.
B
A
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Y6 Weather III
Brambletye Geography Department
Glossary
Term
Definition
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Brambletye Geography Department
Term
Definition
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Brambletye Geography Department
Windy Wordsearch
 There are 25 words or phrases hidden in the grid below.
 Find them and make sure that they are in your glossary with a suitable definition.
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