Download Weather and Climate KSM

WEATHER AND
CLIMATE
•
This PowerPoint summarises the key facts you need to
know for your exam.
• This PowerPoint does not cover case study information
CLIMATE OF THE UK
Weather and Climate
• Weather – day to day weather (precipitation, wind,
sunlight hours) conditions.
• Climate – average weather conditions gained over the
last 30 years. What we expect it to be like for the time of
year.
• Climate statistics we are using at the moment cover the
1961–1990 period
Describing the climate of the UK
Temperature
Rainfall
Sunshine hours
• Highest: July – Aug
(19°C)
• Lowest: Jan – feb
(6°C)
• Range 13°C
• Highest: Oct – Jan
(120mm month)
• Lowest: April – July
(70mm month)
• Fluctuates Febmarch
• Highest: May – Aug
(170-180 hours per
month)
• Lowest: Dec – Jan
(40 hours per month)
Reason:
• Temp and sunlight hours due to Latitude (distance from the equator
• Rainfall reliable all year round due to our Maritime location (island
surrounded by the ocean) and low pressure belt.
Explanation
1. Why is temperature higher in the summer months?
2. Why do we have longer days from May - Aug?
3. Why is rainfall higher in the winter months? (This
question you will be able to answer later on in the
unit)
The earths tilt effects temperature and
sunlight hours
Suns position on 21st March and 21st
September (Equinox)
Suns position on the 21st June
Summer Solstice
Summer Solstice
Suns rays are more direct, therefore it covers a smaller surface area and is more
concentrated leading to warmer temperatures
Suns rays has more atmosphere to travel through
Suns position on the 21st December
Winter Solstice
Winter Equinox
Suns rays is at an angle, therefore it covers a larger surface area and is less
concentrated leading to cooler temperatures
Suns rays has more atmosphere to travel through
Why is temperature higher in the summer months
and lower in the winter?
• In the winter, the North Pole is a little further from the Sun,
and so the sunlight hits the North Pole at more of an
angle, and it has more of the Earth's atmosphere to go
through before it gets to the Earth. That lets the area
around the North Pole get colder.
• In the summer, the North Pole is pointed more toward the
Sun, and so the part of the Earth near the North Pole gets
more direct sunlight, and becomes warmer.
Why do we have longer days from April to September?
• This tilted axis is also the reason why there are more
hours of daylight in the summer and fewer hours of
daylight in the winter.
• In the winter, the closer you are to the North Pole, the
shorter the days are. At the North Pole, it's just dark all
winter.
• In the summer, the closer you are to the North Pole, the
longer the days are. At the North Pole, it is light all
summer, with no nights at all.
Climate of the UK - Annual temperature
• North is cooler than the
south
• This is due to LATITUDE
(Earths tilt that was
explained earlier)
• Upland areas are cooler
• This is due to ALTITUDE.
The higher up you go the
thinner the air so less heat
energy is stored
Climate of the UK - Annual Rainfall
• Highest over mountainous
areas
• ALTITUDE- Air is forced to
rise above upland areas. The
air then cools and condenses
to produce precipitation
• West receives more rainfall
than the east.
• The UK’s most prevailing
WIND DIRECTION is from the
SW. This brings warm moist
air onto land.
Climate of the UK – Rainfall all year round
• We receive rainfall all year
round. This is due to
PRESSURE.
• We lie very near to the low
pressure belt. This means
that air is rising and
condensing producing
rainfall
• The weather systems
(known as depressions
comes from the west. This
is also why the west is
wetter than the east.
Climate of the UK - Annual sunlight hours
• The south and east
have longer hours of
sunlight.
• This is due to less
cloud cover – more
clear skies
• Low lying land – less
shade provided by
hills/mountains
• Sun rises in the east
and sets in the west
Cloud Types
Image
Description
Weather Conditions
Long, thin, wispy streamers. Consist of
Associated with heavy showers,
ice crystals due to the height of the cloud thunderstorms, hail
Fluffy heap cloud that looks like
They can be associated with light rain or
cauliflower. Can consist of ice and water scattered showers depending on the
droplets
height of the cloud. Lower the cloud the
higher the risk of rainfall
A towering vertical raincloud with a black Predict fair weather. No precipitation
base. Contains water droplets in the
lower levels of the cloud and ice crystals
in the upper.
A thick, dark grey-black low lying cloud. A Associated with drizzle
sheet of continuous cloud cover.
Contains water droplets
Grey layer, sheet like cloud. Contains
water droplets
Continuous rainfall
Formation of a depression
• The UK’s depressions begin to form over the Atlantic
where COLD POLAR AIR moving south meets WARM
TROPICAL AIR moving north. Like oil and water, warm and cold air
masses don’t mix!
The boundaries between warm and cold
air (where they meet) are called
FRONTS!
Low
pressur
e
Formation of a depression
• Having started to form over the Atlantic, a depression will
then pass across the UK from WEST to EAST, driven by
the prevailing winds
Development of a depression
L
L
L
L
Warm Fronts – warm air meeting cold air
• Warm fronts occur when
•
•
•
•
light, warm air meets cold
air.
The warm air rises over
the cold air as they meet.
As the warm air rises it
cools and condenses to
form clouds.
Rain falls along the front
as long periods of drizzle
or steady rain.
The symbol on a weather
map for a warm front is
made up of red semicircles along a line.
At 7 pm the
weather will
be....
At 1 pm the
weather will
be....
Cold Fronts – cold air meeting warmer air
• Cold fronts form when cold
•
•
•
•
air moves towards warm air.
The cold air undercuts the
warmer air in front of it,
forcing the warm air to rise
above it more extremely
fast.
As the warm air rises much
faster it may cool more
rapidly and may form large
cumulonimbus clouds.
Heavy rainfall may result
and the air temperature may
become noticeably cooler as
the cold front passes by.
A cold front is symbolised on
a weather map by blue
triangles along a line.
At 3pm the
weather will
be....
At 6am the
weather will
be....
Depressions - Weather conditions
Reasons for the weather conditions
experienced in a depression
• Precipitation at the warm front
• Warm topical air, being less dense, rises above the cooler air. This air
•
•
•
•
•
•
•
•
then cools and condenses forming clouds and then precipitation
Precipitation at the cold front
Cooler polar air from the north meets the warmer tropical air from the
south. As the polar air is cooler it is more dense so undercuts the
warm air forcing it up very quickly to form cumulonimbus clouds and
heavy rainfall
Warmer temperatures in the warm sector
Air is from the tropics (called tropical maritime)
Cooler temperatures in the cold front
Air is from the north (polar maritime)
Strong winds and the passage of the warm and cold fronts
As the warm air is forces to rise at the fronts it creates an area on
lower pressure at the surface, this means that air rushes in to fill the
low pressure gap. The movement of the air generates winds.
Identifying Depressions: Isobars
Identifying Depressions: Isobars
Isobars are lines on a weather
map joining together places of
equal atmospheric pressure.
If pressure decreases towards
the centre it’s a depression
On the map the isobar
marked 1000
represents an area of
higher pressure
While the isobar
marked 988 represents
an area of lowest
pressure.
K. Roberts
Anticyclones - Temperature
Winter
Summer
 Cold day time
 Hot day time temp,
temps, from below
0oc to 5oc
 Very cold night
time temps – frosts
below 0oc
over 25oc
 Warm night time
temps. May not fall
below 15oc
K. Roberts
Anticyclones – Cloud Cover
• Generally clear skies by day & night
Anticyclones – Wind
• Gentle breezes only as air blows out of the system
not into it.
K. Roberts
Anticyclones - Precipitation
Winter
 low level cloud may linger
and radiation fog may
remain in low lying areas
 If temperatures remain
low frost will persist
throughout the day, at
night more frost will
appear. If this lasts for
days it results in a ‘BIG
FREEZE’
Summer
 Hazy sunshine in some
areas
 Early morning mists
which disperse quickly
as the sun warms the
land and air around it
 Heavy dew in the
mornings
 Thunder storms can
occur when Humidity is
high
Reasons for weather in an Anticyclone
Weather condition
Reason
Temperature – Cold in the winter
Long hours of darkness, no clouds to act as a
blanket so heat is lost
Sun shines from a lower angle in the sky and we
have very short daylight hours
Temperature – Warm in the summer
Long hours of daylight, cloudless skies we
receive maxim insolation.
Very light winds
Gentle pressure gradient. Which means there is
very little pressure change over a wide area
Dry weather/ No cloud cover
Air is sinking therefore warms not cools
Warm air can hold more moisture
Precipitation/ Fog /mist
Radiation fog forms on cold nights when the
ground is cool, this causes the air above it to
condense
Frost
Due to increase heat loss and night (no cloud
cover) ground temperatures fall. Any moisture in
contact with the ground condenses and turns into
ice.
Identifying Anticyclones
• Pressure increases towards the centre
• Isobars are further apart (gentle pressure gradient)
EXTREME WEATHER
EVENTS
Weather events in the last 10 years
Case Study of an extreme weather event
In Case study booklet
Evidence for global climate change
Hockey Stick Graph
The Hockey stick
graph shows
temperature
variations over the
last 1000 years
Grey areas are
areas of uncertainty
– because we use
different sources of
evidence the
temperature
readings vary
Hockey Stick Graph- evidence FOR!
Medieval warm period and little ice age caused before cars
and power stations
Sustained
temperatures for
around 1000 years,
then a sharp
increase around
1900. Seen by
many as proof that
humans have
influenced our
current climate
Hockey Stick Graph – RELIABILITY??
HOWEVER.....
Accurate temperature
recordings only go back
150 years
Temperature gained from a
range of sources such as
tree rings ice cores etc.
Assessing the Evidence for Global
Warming
Instrumental readings
• Thermometers have been used to keep a
record of temperatures (post 1850).
• Most of the warming has occurred since
the 1970s, with all 10 of the warmest years
occurring in the past 12 years.
• Average global temperatures have
increased by 0.5C since 1980.
• However the figures are not entirely
reliable due to vegetation growth/decline
that can impact sites. We only have
accurate temperature recordings over the
last 150years or so.
2
Assessing the Evidence for Global
Warming
• Glacial Retreat
• Glaciers are retreating almost everywhere
around the world — including in the Alps,
Himalayas, Andes, Rockies, Alaska and
Africa. Greenland lost 150 to 250 cubic
kilometres (36 to 60 cubic miles) of ice per
year between 2002 and 2006,
• Antarctica lost about 152 cubic kilometres
(36 cubic miles) of ice between 2002 and
2005.
• Up to 25% of global mountain glacier ice
could disappear by 2050
• However this retreat may not be caused
by increased global temperature but could
be due to snow melt.
Assessing the Evidence for Global
Warming
Arctic Ice Cover
• Artic ice over the last 30 years
has thinned to half its
thickness.
• This can speed up warming as
less ice will mean less solar
insulation reflected and more
absorbed by the ocean.
• There are concerns that in a
few years the Artic will be
completely ice free in the
summer months
Assessing the Evidence for Global
Warming
Ice cores
• This is the scientific study of deep ice cores
extracted from Greenland and Antarctica.
• When snow falls year on year it builds up a
record. Trapped water molecules and air can be
analysed to give us an idea of past
temperatures and gases present.
• Scientists from the Antarctic Survey
(Cambridge) have found clear evidence of rapid
increase in temperature in recent decades.
• However ice cores can only be obtained from
certain areas of the world, therefore only reflect
climate changes in those locations.
Assessing the Evidence for Global
Warming
Early Spring
• In the last 30 years there have been
signs of seasonal shifts, spring arriving
earlier for example. Bulbs such as
crocuses and daffodils are flowering
earlier, birds nesting earlier.
• Winters appear to be less server.
• However, could this be due to seasonal
shifts not global warming?
Causes of Global Climate Change
Greenhouse Gas
% (Importance) to the
greenhouse gas layer
Human Sources

Carbon Dioxide
60%




Methane
Nitrous Oxides
20%
Very small concentrations
but up to 300 times more
effective at trapping heat
Burning fossil fuels (coal, oil, gas) to produce electricity
or in industry.
Car Exhausts
Deforestation
Burning wood



Decaying organic matter in landfill sites and compost
heaps
Rice farming
Farming Livestock(cows)
Burning Biomass for energy




Car Exhausts
Power stations producing electricity
Agricultural fertilisers
Sewage treatment
Cause – The Greenhouse effect
• The sun’s rays reaches the earth as
•
•
•
•
•
Shortwave radiation. Known as Visible
Light
The shorter the wave the higher the
energy. This is able to get through the
greenhouse gas layer easily.
The shortwave radiation from the sun is
reflected or absorbed.
The Reflected radiation remains as
shortwave radiation, this has the energy to
escape through the greenhouse gases
back into space
If it is absorbed the object that it hits begins
to warm. The warm objects -then re-emits
long -wave radiation known as Infra-red.
The absorbed radiation is now released as
long wave radiation that has less energy
and so only some will escape. The rest will
be re absorbed by the earth’s atmosphere,
keeping us warm, this is GOOD (14deg c
rather than -17 deg)
Cause – The ENHANCED Greenhouse
effect
• Humans are increasing
the amount of
Greenhouse gases in the
atmosphere. This means
that less and less longwave radiation can
escape back into space.
• More and more long wave
radiation is being
absorbed by the
atmosphere increasing
world temperatures. This
is BAD!!
IMPACTS AND
RESPONSES TO GLOBAL
CLIMATE CHANGE
Impacts – On UK and the WORLD
Responses – Local, national and international
In Case study booklet
Cause/ Formation of tropical cyclones
• Develop of sea water that’s 27°C or higher
• Happen in late summer early autumn when sea
temperatures are at their highest
• Need ocean depths of 70m or more, therefore
lose strength in shallow waters and when they hit
land
• Occur between 5°North and south of the equator
where the earths rotation (coriolis effect) deflects
the path of the winds and cause the storm to spin.
How do Tropical cyclones form?
This then creates a Tropical Storm (Cumulonimbus clouds)
With increasing moisture and convergence of wind it fuels
the storm. When winds speed become above 74 mph it is
classified as a tropical cyclone
The movement of this air creates winds
The air is
Warm
warmed
air and
water
againvapour
and
rises
This Results in Low
pressure/ meaning
less air resting on
the earths surface
Coolerair
air
Cooler
rushesininto
tofill
fill
rushes
thethe
gap
again
gap
Warm air from
thunderstorms and
from the surface of
the ocean, combine
and begin to rise
causing low pressure.
The warm air rises faster and
faster, this encourages more
warm air to be sucked up into
the storm, but it also sucks
cooler drier air down.
As the hurricane
moves across the
ocean, it picks up
more moisture and
increases its speed.
http://news.bbc.co.uk/1/hi/sci/tech/4588149.stm
Trade winds (winds
moving into the low
pressure) cause the
storm to rotate in an
anti-clockwise
direction.
This is the eye of the
storm, an area of low
pressure and calm
conditions.
Located just
outside of the eye
is the eye wall.
This is the location
within a hurricane
where the most
damaging winds
and intense rainfall
is found
The outer edge of the
Hurricane is a
spiralling vortex or
rain bands. It has high
rainfall and high
winds.
eye
anticlockwise spin
Exam question – label
features of a Tropical
cyclone (4 marks)
eye
wall
spiralling/outer rain bands
continuous cloud
cover
broken cloud
cover
circular shape
very large size
Weather - Approach of a hurricane
Weather - The Eye Wall
Weather - The Eye
Weather - The Eye Wall Part 2
Weather The End...
CASE STUDIES OF TROPICAL
CYCLONES IN A RICH PART OF
THE WORLD AND A POOR PART
OF THE WORLD
Katrina (USA) – Effects and responses
Nargis (Burma) – Effects and responses
In Case study booklet