Transcript Y7GeU2B Weather typesPP Wk4

What are the different types of
weather
How do we
measure
weather?
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Today we will look at …
1.
2.
3.
4.
What makes weather?
How do we measure weather?
Why do we need forecasts?
Are the forecasts any good? (that’s
homework)
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What is the weather?
Weather is the condition of the
air around us over a short period
of time (from day to day)
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The elements of weather
Temperature (the amount of heat)
Precipitation (water – rain, sleet, hail,
snow)
Wind speed
Wind direction
Clouds
Air pressure
Visibility (How far can you see?)
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Temperature
This is a measure of
how hot or cold it is.
We can tell this by
looking at the
clothes that people
wear.
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Precipitation
Water in the air falls
to the ground in one
of several forms
Rain
Snow
Sleet
Hail
But also ice and fog
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Wind Speed
This tells us how
strong the wind is.
We can get a good
ideas of this by
looking at smoke
and trees.
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Wind direction
This is the
direction from
which the wind
blows – it is
measured by a
wind vane
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Cloud Type
Clouds come in many
shapes, sizes and
heights – more about
that next week
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Cloud Cover
This is the amount of
the sky covered by
cloud. It is
measured in eighths
Clear sky
4/8
8/8 (Total cover)
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Visibility
This is the distance
that can be seen. It
is measured in
metres.
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Measuring Weather
Who else might
find a forecast
useful?
Why do we measure the weather?
Weather can be described using terms such as wet or
fine, warm or cold, windy or calm, so why is there a
need to measure the weather?
For most people, a description of the weather is
adequate but for many businesses more detailed and
accurate measurements are required.
The science of studying weather is called meteorology.
Weather scientists or meteorologists measure
temperature, rainfall, pressure, humidity, sunshine and
cloudiness and they make predictions and forecasts
about what the weather will do in the future.
This is important for giving people advance notice of
severe weather such as floods and hurricanes – or even
‘Can I go out without my raincoat tomorrow?’
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Measuring temperature
The hotness or coldness of a substance is called its
temperature and is measured with a thermometer. The
ordinary thermometer consists of a hollow glass bulb
attached to a narrow stem with a thread-like bore.
The bulb is filled with liquid,
– If it is silver it is mercury
– If it is red it is alcohol
The liquid in the tube expands when the temperature
rises and contracts when the temperature falls. The
amount of expansion and contraction is measured by a
numbered scale.
Whilst thermometers are really measuring their own
temperature, they are used to measure the
temperature of the surrounding air.
To make sure that the temperature of the surrounding
air is the same as the thermometer, it must be shaded
from sunlight and be exposed to adequate ventilation.
These conditions are provided by a Stevenson screen. 13
A Stevenson screen
Why do we
need one of
these?
What are
the little
gaps in the
side for?
(louvers)
Why does it
have legs?
Why is it
painted white?
Why has it got such a
large roof?
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Measuring temperature
Most temperature scales today are
expressed in degrees Celsius (°C),
although you will sometime see
Fahrenheit (°F) in use.
The Celsius scale is fixed by two points,
the freezing and boiling point of water,
which at sea level are 0°C and 100°C
respectively.
The scale is then divided into 100 units.
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Measuring Temperature
This is a maximum-minimum thermometer.
This type of thermometer measures both the
highest (maximum) and lowest (minimum)
temperature over a period of time, usually one
day (24 hours).
Recording temperature with a maximumminimum thermometer
There are two markers, one for the maximum
temperature and one for the minimum. The
mercury in the tube pushes the markers as
temperatures go up or down.
The temperature tends to be highest around the middle of the day,
when the sun is at its highest in the sky – even if you cannot see it
because it is cloudy
The temperature is coldest during the night
So if you leave a maxi-min thermometer for 24 hours you will get
the maximum and the minimum and be able to find the daily range
(the difference between the 2) or the diurnal range.
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Looking at the first 2 rows on the
WS
What does a thermometer do?
How does it work?
What does a maxi-min thermometer tell
you?
What is diurnal range?
What does a Stevenson screen do?
How does it work?
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Wind speed
Wind is moving air.
Wind can be measured by its speed
and the direction from which it has
come.
The speed of the wind can be
measured using a weather instrument
called an anemometer.
The number of turns it does is
translated into speed which can be
recorded in a number of different
ways:
–
–
–
–
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miles per hour;
kilometres per hour;
metres per second;
Knots ( a measurement sailors use)
the Beaufort Scale (we will learn about
this one next week)
This one has
a weather
vane on it
underneath.
What does
that tell
you?
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Wind direction
The direction of the wind is
expressed as the point on the
compass from where the wind is
blowing.
If a wind is blowing from the south,
it is travelling northwards but is
called a southerly wind.
Wind direction can be measured in
many different ways; using a weather
vane or windsock or simply holding a
light object such as a flag or ribbon.
http://www.bbc.co.uk/schools/whatis
weather/aboutweather/winddir.shtml
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Wind direction
Knowledge of wind direction is important
for many people and activities.
For example aircraft need to take off
from the end of the runway which is
going into the wind for extra lift at
take-off
Wind direction is of course very
important for leisure activities such as
yachting.
Can you think of anything else where
knowing the wind direction is important?
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For the WS…
What is an anemometer for?
How does it work?
What is a weather vane for?
How does it work?
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Air pressure
An instrument called a
barometer is used to
measure the pressure of
air.
Although air is very light,
because the atmosphere is
so thick (many kilometres in
altitude above the Earth's
surface), air exerts a force
or pressure.
When air is cooled it sinks
towards the ground, the
pressure increases and a
high pressure is measured.
When the air warms up it
rises, the pressure is
reduced and low pressure is
measured.
This is what goes on
inside a barometer
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Air pressure
Why do we need to know
about pressure?
High pressure gives us
clear skies which means it
is hot in the summer and
cold in the winter
Low pressure gives us
cloudy skies and rain. We
have lots of low pressure
over the summer in the UK!
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For the WS
What is a barometer for?
How does it work?
What is weather like if the pressure is
high in summer?
What is the weather like if the pressure
is low?
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Measuring liquid precipitation
What varieties of precipitation are
there?
Which types are NOT liquid?
Why do you think that if we measured
this one, that we might not use the same
instrument as the liquid one?
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This is the rain gauge used by the
Met Office
Why do you think the
actual funnel is inside
a copper cylinder –
not a the top?
Why is the bottle
that stores the water
underground?
How does the
measuring gauge on
the right work?
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For the WS…
What is a rain gauge for?
What kind of precipitation does it not
collect?
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Weather is important to us
Things that are affected by weather
–
–
–
–
–
–
farming
sport
transport
the amount of energy we use
work
tourism
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So we need weather forecasts
Information is
collected by
– weather stations
– http://www.weatherst
ations.co.uk/aws_map.
htm
Often schools have
them
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So we need weather forecasts
Information is also
collected by
By ships
Aircraft
Satellites
and then the
meteorologists use
the information they
have to predict the
weather over the
next few days
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Symbols are
different but
once you get the
idea…
So what is the
weather
supposed to be
like in each of
these places?
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Homework
If it is the UK, click
on your region
Do not go more
detailed than that
If a continent, pick
which part, then pick
your country
Go to (hopefully now!)
http://www.weathero
nline.co.uk/
Click either UK or
your continent
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I am doing South
Africa
I clicked on Africa on previous link
and got this:
I clicked on Southern Africa and
got the dropdown
Then I clicked on South Africa and
saw this:
But I don’t want today – I want
the next 5 days which are tabs
above the maps.
This one shows a Monday, so I
would copy and paste Tuesday to
Saturday.
So if I click on Tuesday, hover
over the map, right-click and copy
image, you can then paste it into
the homework document.
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Now you have got your weather
forecast
Look out each day – how good was the
forecast?
If you have a thermometer, do use it and
add that information in!
If you haven’t, not to worry.
Having put your pictures into the table
Record the weather you had in the
middle column
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Now you have got your weather
forecast
In the last column, comment on whether
the weather forecast was completely
rubbish, pretty good or spot on –
Remember to give your opinion and then
add a ‘because…’.
For example:
The weather forecast was completely
wrong, because the forecast said it
would snow when really there was mostly
sunshine with a few clouds.
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