Weather and Climate

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Weather and Climate
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You will find the following topics in this
Slideshow

• The difference between weather and climate.
• Microclimates (including the role of aspect,
  shelter, buildings, surface and natural features)
• The global water cycle (including interception,
  surface run-off and infiltration)
• Types of Rainfall (Relief, Convectional,
  Frontal)
• Temperature and rainfall variations in the
  British Isles (and what causes them).

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Weather
Weather is the condition of the atmosphere in a
place at one moment. It can change from one
second to the next.
Weather includes rainfall, temperature,
visibility, wind speed, wind direction and cloud
cover.
Climate
Climate is the average weather in a place
measured over 30 years. It is what we expect in a
place.
Climates include Mediterranean, Polar, Temperate,
Hot Desert and Equatorial.
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Microclimates
A microclimate is a small area where the climate
is different to the surrounding area.
They can be affected by
SHELTER
ASPECT
NATURAL FEATURES
BUILDINGS
SURFACE
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This is the direction a place faces. Places that
face the sun are warmer than those that face away
from the sun. In the UK (where Common Entrance is
written) places with a south-facing aspect get
more sun and higher temperatures.
ASPECT
These can change wind speed and direction,
creating either calm or very windy areas. On
warm, sunny days, buildings absorb heat and give
it out at night. This means that cities can have
night-time temperatures 2-3C warmer than areas
outside the city.
BUILDINGS
SHELTER
Walls, buildings, cars, hedges and trees provide
shelter from wind. Sheltered places often feel
warmer and also get less rain. Lakes and their
shores are often more windy than surrounding
areas.

NATURAL FEATURES
SURFACE
Dark, artificial surfaces like tarmac warm up
faster and give off more heat than light, natural
surfaces like grass.
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The Global Water Cycle
Infiltration
Groundwater flow or Through flow.
Interception
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Water Cycle definitions
Evaporation is the process of water turning into
water vapour due to warming.
Transpiration is evaporation from tree leaves or
plants.
Precipitation is rain, drizzle, snow, sleet or
hail.
Condensation is where water vapour cools and
turns back into water. In this case it happens
high up and forms clouds.
Interception is where precipitation lands on tree
leaves etc. and so does not reach the ground.
Infiltration is where the water sinks into the
ground prior to experiencing Groundwater flow.
Groundwater flow or Through flow is where water
flows downhill under the surface.
Surface run-off (or overland flow) is where water
flows downhill overland, mainly in rivers.
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Types of Rainfall
There are 3 types of rainfall
1. Relief Rainfall
2. Convectional Rainfall
3. Frontal Rainfall
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1. Relief Rainfall
4. Condensation occurs and clouds are formed.
5. Precipitation.
3. Air cools as it rises.
2. Air is forced up by high land.
1. Warm, moist air blows in from the sea.
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2. Convectional Rainfall
4. Condensation forms clouds
5. Precipitation
1. Suns energy heats up the earth
3. Warm, moist air cools as it rises
2. Evaporation and transpiration
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3. Frontal Rainfall
4. Condensation forms clouds
5. Precipitation
3. Warm, moist air cools as it rises
2. Warm air rises over the cold air as it is less
dense
1. Warm air and cold air meet at a front
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Temperature and Rainfall in the British Isles
Facts about the British Isles climate
Wet Mild Winters Mild Summers
1. The west is wetter than the east all year
round.
Summer prevailing wind
Dry Cold Winters Mild Summers
2. In winter, the west is mild and the east is
cold.
Dry Cold Winters Warm Summers
Wet Mild Winters Warm Summers
3. In summer, the north is mild and the south is
warm.
Winter prevailing wind
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What causes these variations?
1. The west is wetter than the east all year
round.
This is because the prevailing wind is always
from the South-West or the West. This brings
moisture off the Atlantic Ocean and the mountains
down the west coast force this upwards to form
relief rainfall in the west. The east is in a
rain shadow and so gets less rain.
2. In winter, the west is mild and the east is
cold.
Again, this is caused by the prevailing wind,
which is from the South-West in winter. This
causes the South and West of the British Isles to
be slightly warmer as the wind has travelled
across the warm Atlantic Ocean to get to Britain.
3. In summer, the north is mild and the south is
warm.
This is due to the distance from the equator. The
north is further away and hence cooler. Also, the
prevailing wind comes in from the west and so
does not have a cooling effect on the south
coast. The north can also be vulnerable to Arctic
winds at times, reducing the temperature there.