Download Weather in the UK

Weather in the UK
Weather is the condition of our atmosphere. This is made
up of temperature, rainfall, windspeed and other elements
which change all the time.
Climate is the average temperature, rainfall and
windspeed in one place. Climate varies across the UK.
Factors which affect temperature in the UK
There are four factors which affect temperatures in the UK:
1. Latitude
2. Aspect
3. Relief
4. Distance from the sea
Latitude
1. Further from the equator the
sun’s rays are at a lower angle and
pass through more atmosphere.
They lose heat among the clouds,
gas and dust.
2. The rays spread out over a
wider area so there is less heat.
Aspect
Aspect is the direction which the land faces. Places facing south are
warmer because:
1. They receive more heat from the sun.
2. They are sheltered from cold northerly winds.
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Relief
Temperature decreases by
1°C for every 150 metres in
height
Distance from the sea
In winter it is warmer in the west of the UK because:
1. The Atlantic is milder than the land surface because water cools more
slowly than land.
2. The North Atlantic Drift (a warm ocean current) makes it even milder.
3. Our prevailing winds come from the south-west and bring warmth
from the Atlantic.
Factors which affect rainfall in the UK
There are three factors which affect rainfall in the UK:
1. Relief
2. Aspect
3. Distance from the sea
Relief
Upland areas receive more rain
than lowland areas because:
1. Moist air blows in from the
Atlantic.
2. The air rises over the hills
and cools down.
3. As the air cools the water
vapour condenses into water
droplets.
4. The water droplets come
together to form clouds
5. The droplets become bigger
and fall as rain.
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Aspect
West facing slopes receive the most rain as the Atlantic is to the west of
the UK.
Areas to the east are in the rain shadow and have less rain as the air is
drier
Distance from the sea
Winds in the west are full of water vapour and bring a lot of rain.
As the winds move eastwards they drop most of their water and become
drier.
Activities
1. As you get nearer to the equator the sun’s rays are warmer, explain
why this is so (include 2 detailed reasons).
2. The land at Shantron farm on Loch Lomond starts at 110m and rises
to 810m. In summer the average temperature at 110m is 16°C, what is
the average temperature at 810m?
3. Choosing from north, south, east and west, which aspect is:
(a)
(b)
(c)
(d)
warmest
wettest
driest
coldest
4. Draw a labelled diagram to explain why it rains more at the top of a
hill than at the bottom.
5. What are the differences in the UK’s weather between the west coast
and the east coast? (Include 4 differences and explain your points)
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Air Masses
The five air masses which affect the UK
are:





Polar maritime (Pm)
Polar continental (Pc)
Tropical maritime (Tm)
Tropical continental (Tc)
Arctic maritime (Am)
Activities
1. Match the descriptions below with the different air masses on your
map:
Comes from Siberia
Very cold, dry weather in winter
Warm, dry weather in summer
Very little wind
Comes from North Atlantic Ocean
Cool, wet and dull weather
Strong winds
Our most common air mass
Comes from tropical Atlantic Ocean
Warm and wet weather in summer
Mild and wet weather in winter
Strong, south west winds
Comes from Norway and Greenland
Very cold, wet weather
Snow in winter, showers in summer
Cold, biting winds
Comes from Sahara desert
Hot and dry in summer
Light winds
2. Rank our five air masses according to their:
a)
b)
c)
d)
summer temperatures
winter temperatures
windspeeds
total precipitation (rainfall)
3. Which air masses will these people want the most and why?
a)
b)
c)
d)
e)
marathon runners
people working in emergency services
travel agents
farmers
white water rafters
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4. Write a short newspaper article or story about one of the following
groups and how they are affected by the given air mass:
a) School pupils skiing in the Highlands of Scotland with a particularly
bad Arctic maritime air mass in January.
b) A RNLI lifeboat attempting to rescue a fishing boat with engine
problems with a Polar maritime air mass in the Atlantic Ocean in
November.
c) Wheat farmers in the south east of England during a prolonged
Tropical continental air mass in August.
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Pressure systems
Low pressure
High pressure
There are two types of pressure system:
HIGH pressure – when air is cold and heavy and is pressing down on the
surface.
LOW pressure – when air is warm and light and rises up into the upper
atmosphere.
Use the following two paragraphs to fill in your air pressure systems
tables:
High pressure systems are called anti-cyclones, pressure within them is
usually above 1000mb (millibars) and there is very little cloud resulting
in a lot of sunshine and little precipitation. Winds tend to be light and
the system spins in a clockwise direction. The weather associated with
high pressure is very cold winters and heat waves in summer.
Low pressure systems are called cyclones or depressions, pressure
within them is usually below 1000mb (millibars) and there is lots of
cloud resulting in little sunshine and lots of precipitation. Winds tend to
be strong and the system spins in an anti-clockwise direction. The
weather associated with low pressure is cool or cold in winter and cool
in summer with lots of wind and rain.
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Depressions
A depression forms in the following way:
 A tropical maritime air mass blows from the south west and a polar
maritime air mass blows from the north east.
 The warm air makes a wedge into the cold air but does not mix, instead
it rises over the cold air, creating an area of low pressure (depression).
 The depression is made up of a warm front (where warm air rises over
cold air), a warm sector, occupied by the warm air, and a cold front,
where cold air undercuts warm air (see diagram above).
 Where the cold air catches up with the warm air an occluded front is
formed.
Activities
1. In which direction
do winds blow in a
depression?
2. What are millibars
and isobars?
3. Draw the symbols
for a warm front, cold
front and occluded
front
4. Give the weather
forecast for places A,
B and C on the map
opposite.
5. Which part of a
depression brings:
a) most rain
b) the warmest
weather
c) the least cloud
d) the coldest winds?
A
C
B
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Practice question:
Synoptic chart for British Isles at
0700h on 31st August.
A yacht race from Wick to
Stornoway was due to start from
Wick harbour at 8:00am on 31st
August.
At 7:00am the Met office advised
the organisers to cancel the race.
With reference to the synoptic
chart, explain why the advice was
given (give 5 reasons).
Centre of low
pressure :
likely to bring
stormy
weather
Occluded front:
broad belt of
very heavy
rain, low cloud
and poor
visibility
South
westerly
winds
Associated
weather is
moving west
to east
Tightly packed
isobars : strong
winds
Cold Pm air
Warm Tm air
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High Pressure systems
Areas of high pressure are called anti-cyclones and they occur where the
air is sinking.
Activities:
1. On your handout add the following labels:
Isobars are widely spaced, giving light winds
Winds blow clockwise and outwards in an
anti-cyclone
Anti-cyclones move more slowly than
depressions, giving settled weather
Dry weather with few clouds because no air
is rising
2. Write out the sentences below, matching the heads to the correct
tails:
Anticyclones are areas of
In high pressure areas the air
is
Because the air is sinking
Because no air is rising
Because there is little rain
Because there is a lot of
sunshine
Because there are few clouds
Because it is hot in summer
Because anti-cyclones move
slowly
Because the isobars are widely
spaced
no air is rising and cooling
there may be thunderstorms
there is plenty of sunshine
winds are very light
it is very cold at night
sinking
the weather is settled
high pressure
the weather is hot in summer
there are few clouds and no rain
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3. Make two lists – one for activities that are helped by anti-cyclonic
weather and one for activities that are hindered by anti-cyclonic weather
How do we forecast the weather?
At weather stations around the world data is collected such as pressure,
temperature and wind speed. This is sent to the Met Office in the UK
where they have a supercomputer which runs complex programmes
which help to predict what the weather will do in the short and long
term.
This collected data can also be shown in weather station circles which
can then be shown on a synoptic chart or weather map.
Activities:
1. What are the six ways of recording weather conditions at different
places?
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2. For the weather stations circles A and B give:
a) the cloud amount (oktas)
b) the temperature (°C)
c) the windspeed (knots) and direction
d) the weather conditions
A
.
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B
-4
2. Do the same for the two station circles on the synoptic chart below.
3. Which one shows the weather in Paris and which one shows the
weather in Inverness?
4. Explain your answer to the above question (include at least 6
reasons)
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