Transcript The climate of the UK

The Climate of the
UK
WHAT IS CLIMATE?
 Some say that climate is what you want, but weather is what
you get!
 If you go on holiday to Majorca in August, you expect it to
be hot and sunny – that’s climate. If it rains, you’ve got
weather.
WEATHER & CLIMATE
 Weather is the short-term day-to-day state of the
atmosphere. It relates to changes in conditions such as
temperature, wind and sunshine.
 Climate is the average of those weather conditions,
measured over thirty years.
MILD AND WET
 The UK’s climate is generally mild and wet. They generally
have a temperate maritime climate, which is influenced
by the sea surrounding the UK. In summer the sea cools the
climate, and in winter the sea insulates the UK – keeping it
warmer than other places at the same latitude.
 However, the UK’s climate is not the same everywhere!
EXPLAINING CLIMATE
 Why is the UK’s climate mild and wet? There are a number
of factors that help to explain it, but the most important
one is latitude.
 The further you go from the equator, the cooler it gets.
Why? Because the Earth’s surface is curved, which means
that the sun’s energy isn’t evenly distributed.
LATITUDE
 The diagram shows how the sun’s energy is much more direct and
concentrated than at the Poles. This means that the earth is hottest
here.
 At the North and South Poles, the greater curvature of the Earth.
means that the sun’s
energy is spread over
a larger area. This
means
colder
temperatures.
Ice
forms
there
and
reflects heat back
into space, making it
even colder.
DISTANCE FROM THE SEA
 The sea is cooler than the land in summer – but warmer in
winter – because it takes longer to heat up than the land, but is
slower to cool down. The sea moderates the UK’s climate,
making temperatures more even throughout the year.
 The interior of countries with large land masses, like the USA,
have a continental climate. It is too far from the sea to be
influenced by it, and so they have very cold snowy winters, and
hot dry summers.
Ocean Currents
 The North Atlantic Drift
is a current of warm
water that flows across
the Atlantic from the
Gulf of Mexico.
 It keeps the coasts of
western UK much
warmer than areas
inland.
ALTITUDE
 Temperature decreases by 1°C for every 100m of altitude
(height above sea level [ASL]). So, mountainous areas are
always cooler. These also tend to get more rain (because of
relief rainfall), so they are wetter too.
Prevailing Winds
 A prevailing wind is the
direction from which the
wind blows most often.
 The prevailing winds for
Europe are from the
south-west.
 The temperature of a
prevailing wind is affected
by the area it blows over
Theses winds bring more rain to western
parts of UK.
WET, WET, WET
 It’s always raining in the UK – or at least that’s how it feels.
 In the UK we get 3 types of rainfall:
 relief rainfall (sometimes called orographic)
 convectional rainfall
 frontal rainfall (we will learn about this next lesson)
RELIEF RAINFALL
 Warm moist air arrives from the Atlantic Ocean and rises over the
mountains on the western side of Britain – the Cambrians, Pennines and
Grampians.
 When it rises, it cools, condenses into a cloud and starts raining. The
mountain peaks can receive a lot of rain – up to 2000 mm a year.
 Once the air has passed over the mountains, it descends and gradually
warms as it reaches lower ground. This creates drier conditions and is
called the rain shadow. Therefore, mountains in the UK tend to be
wetter in their windward, western sides and drier on their leeward,
eastern sides.
RELIEF RAINFALL
RELIEF RAINFALL
CONVECTIONAL RAINFALL
 During the summer, strong sunshine causes the ground to heat up
rapidly. This sets up rising pockets of warm air, known as convection
currents.
 The warm air rises rapidly to a high altitude, where it cools and its
water vapour condenses to form clouds.
 With time, particularly late afternoon, thick cumulonimbus clouds can
form. These can produce heavy rainfall and sometimes thunderstorms.
Therefore, some places like Cambridge have their wettest months in
July or August.
CONVECTIONAL RAINFALL
PRESSURE AND WINDS
 Around the world some areas have high pressure and some have low
pressure.
1. The UK is in a low-pressure zone. Air is rising here.
2. Air cools, condenses and forms clouds – then it rains and the UK gets
its wet weather.
QUESTIONS
1. Explain how latitude affects the climate of the UK.
2. Explain how distance from the sea affects the climate of the
UK.