Transcript 3. Atmosphere

1. Global heat budget
2. Redistribution of energy by
atmospheric and oceanic
circulation
3. Cause and impact of the
Intertropical Convergence Zone
(ITCZ)
The atmosphere was formed as the Earth cooled and it now
envelopes the Earth. It is made up of a mixture of gases and
gives us life, making our planet unique and distinctive.
The Global Heat Budget
The Global heat budget is the balance
between the incoming and outgoing solar
radiation.
Incoming solar radiation is also called
INSOLATION. It is received in the form of
short-wave energy.
The Global Heat Budget
Short wave solar radiation (insolation) enters the Earth’s atmosphere.
24% of this energy is reflected by clouds and the Earth’s surface (ice
and snow). 6% is scattered by gases in the atmosphere.
In total 30% of radiation is reflected by albedo (the reflectiveness of a
surface).
19% of radiation is absorbed by clouds, water vapour and dust.
Only 51% of the radiation is absorbed by the Earth’s surface.
This heat is then reflected as long wave (infra red) radiation.
6% of this energy goes out into space and 94% is absorbed by water
vapour, CO2 and other greenhouse gases (methane, nitrous oxide). It
is then re-radiated.
Without these greenhouse gases Earth would be 30°C cooler.
The Global Heat Budget
Latitudinal Variations in the Energy Balance
The Global Heat Budget
Latitudinal Variations in the Energy Balance
Study the graph showing latitude and energy balance, note down the following
point and then answer the questions that follow:
Between approximately 35°N and 35°S there is a surplus of energy because
incoming solar insolation exceeds outgoing radiation.
1. Is there an energy deficit or surplus polewards from 35°N/S?
2. At what latitudes is there an energy balance?
3. What is the terrestrial radiation:
a) At the poles
b) At the equator
4. What is the solar insolation:
a) At the poles
b) At the equator
WHY?
The Global Heat Budget
Latitudinal Variations in the Energy Balance
Look at the diagram in pairs and discuss reasons why tropical
areas receive more solar insolation than polar areas
Use the following clues to help you:
1. Compare the dotted lines where Q and P strike the Earth
2. Compare the amount of atmosphere Q and P travel through
3. What other differences are there between the tropical areas
and polar areas that might affect the amount of insolation they
get (hint ALBEDO)?
4. Are there any seasonal effects?
The Global Heat Budget
1. The Sun’s rays are more concentrated at the equator
and more spread out at the poles due to the strike angle
so there is less insolation at the Poles.
2. In Polar regions, there is a greater amount of
atmosphere to pass through, so more insolation is
reflected or absorbed by clouds and dust.
3. Light coloured surfaces (snow) reflect heat back into
the atmosphere (high albedo). Rainforests are dark and
absorb heat (low albedo).
4. Due to the tilt of the earth the poles receive no solar
insolation for several months whilst the sun is directly
overhead all year round at the equator.
REDISTRIBUTION OF ENERGY BY ATMOSPHERIC AND OCEANIC
CIRCULATION
Energy is transferred from lower latitude energy
surplus areas to higher latitude energy deficit areas
by atmospheric circulation. If there was no
atmospheric circulation, lower latitudes would get
hotter and hotter and higher latitudes colder and
colder.
Cold air descends giving
areas of high pressure.
activeboard
Hot air rises
creating areas of
low pressure
Air moves from
areas of high to
low pressure
ATMOSPHERE
THE THREE
CELLS
TOGETHER
Polar Cell
Ferrel Cell
Hadley Cell
Hadley Cell
Ferrel Cell
Polar Cell
ATMOSPHERE
CELLS AND HEAT TRANSFER
A single cell model like in diagram 9 is too simplisticthere are three interlinked cells!
THE THREE CELL MODEL;-FORMATION OF THE HADLEY CELL (1)
At the Equator warm
air rises and travels to
the poles.
INSOLATION
SOLAR
ENERY
ATMOSPHERE
FORMATION OF THE HADLEY CELL (2)
NORTHERN HADLEY CELL.
The air cools and
begins to fall 30ºN
and S of the Equator.
Cooled air returns to
the Equator. This is
the Hadley cell.
SOLAR ENERGY
SOUTHERN HADLEY CELL.
ATMOSPHERE
FORMATION OF THE POLAR CELL (1)
Cold, dense air
sinks at the poles
and moves towards
the Equator.
ATMOSPHERE
FORMATION OF THE POLAR CELL (2)
At about 60ºN and 60 ºS,
the cold polar air begins to
warm.
NORTHERN POLAR CELLS.
This warm air rises and
returns to the pole,
carrying heat energy.
SOUTHERN POLAR CELLS.
This is called the POLAR
CELL.
ATMOSPHERE
FORMATION OF THE FERREL CELL
The Ferrel Cell is
caused by friction
between the other two
cells.
The Hadley Cell draws
cool air down at 30ºN
and S and the Polar Cell
sends warm air up at 60ºN
and S.
ATMOSPHERE
THE THREE
CELLS
TOGETHER
Polar Cell
Ferrel Cell
Hadley Cell
Hadley Cell
Ferrel Cell
Polar Cell
ATMOSPHERE
The climatic
zones associated
with the cells
Polar Cell
Ferrel Cell
Hadley Cell
Hadley Cell
Ferrel Cell
Polar Cell
THE TRANSFER OF HEAT ENERGY FROM
EQUATORIAL TO POLAR AREAS
Where air carrying energy from the
Equator in the Hadley Cell comes into
contact with air in the Ferrel Cell, there
is a transfer of heat energy into the
Ferrel Cell.
There is a similar transfer of
heat energy from the Ferrel
Cell to the Polar Cell.
SOLAR ENERGY
In this way, heat energy is
transferred from the Equator,
where there is a surplus of energy,
to the poles where there is a
deficit.
19
THE CORRESPONDING MOVEMENT OF COLDER AIR
In the Polar cell cold air from polar
regions flows to mid-latitudes as polar
easterly winds
In the Ferrel Cell there is a
movement of cold air at high
altitude.
In the Hadley Cell, cooler
air moves from the subtropics to the Equator.
Q
20
Ocean
Currents
and Heat
Transfer
AIM: To be able to DESCRIBE and EXPLAIN
the pattern of the earth’s major ocean
currents.
The oceans receive about 70% of the sun’s insolation
and the ocean currents play an important part in
redistributing this energy.
1. Shade in the arrows RED and BLUE to show the warm
and cold currents.
2. Label the currents A to F next to the map.
DESCRIBING ocean currents:
Look at the currents in the Atlantic Ocean……..
Describe the movement of ocean currents in the North Atlantic gyre.
EXPLAINING what influences the ocean
currents……..
1. Prevailing winds….
Surface ocean currents directly respond to prevailing winds e.g. the
westerlies in the Atlantic help direct the Gulf Stream and North Atlantic Drift.
2. Coriolis force…..
This deflects the currents RIGHT in the northern hemisphere and LEFT in
the southern hemisphere.
3. Land masses….
Currents are blocked and deflected by continental landmasses setting up
roughly circular loops or GYRES – clockwise in the northern hemisphere
and anticlockwise in the southern hemisphere. The exception is the
Antarctic circumpolar (west wind drift) – WHY?
4. Temperature difference…..
Cold water is denser and therefore sinks and travels towards equator. Warm
water less dense so rises to surface and flows away from the equator. A
convection cell is created.
The Intertropical
Convergence
Zone (ITCZ)
ITCZ CASE STUDY: WEST AFRICA
Label the following countries on your maps: NIGERIA, BENIN, TOGO, GHANA, COTE
D’IVOIRE, BURKINA FASO, MALI, NIGER
Shade in
the
rainfall
amounts
and
include a
key for
your map.
Shade in
the
vegetation
types for
the case
study area
and
include a
key.
High annual
temperatures with little
variation throughout
the year. Rainfall
throughout the year
can often exceed
2000mm often with
two maxima.
High temperatures with a
bigger temperature range
giving a cool, dry season; a hot
dry season and a hot wet
season. Sometimes called
savanna.
Areas receive less than 250mm rainfall a year.
Temperatures range from 15 - 35°C.
EQUATORIAL
DESERT
TROPICAL
ITCZ – the two main air masses.
AIR MASSES
North east
trade winds
An air mass is an
extensive body of air
that is influenced by
the earth’s surface.
Those developing over
oceans generally hold
more water vapour.
South east
trade winds
Add the two arrows to your 2nd map
1. The ITCZ is the
meeting point of a hot,
wet and unstable tropical
maritime air mass (mT)
from the Gulf of Guinea
(south east trade winds)
and a hot, dry and stable
tropical continental (cT)
air mass from the Sahara
desert (north east trade
winds) also know as the
Harmattan winds. Where
the air masses meet
warm air rises,
condenses and causes
heavy rain.
1. Where this happens warm air rises,
condenses and heavy rain falls.
2. The meeting point
of these two air
masses moves north
when the sun moves
north of the equator
(June) and it moves
south when the sun is
overhead south of
equator (December)
because of the tilt in
the earth’s axis. It is
known as the thermal
equator.
ATMOSPHERE
S
IN JUNE
Compare the January and July diagrams.
Hot
dry
cT
air
Wet
warm
mT air
Moves this way
HEAVY RAINS
Gulf of
Guinea
Coastal
areasequatorial
climate
N
‘Harmattan’ wind
LIGHT RAINS
Inland areassavanna
climate type
SaharaDesert
climate
type
ATMOSPHERE
S
Hot
wet
mT air
IN DECEMBER
N
Hot
dry
cT
air
Moves this way
‘Harmattan’ wind
HEAVY RAINS
Gulf of
Guinea
Coastal
areasequatorial
climate
Inland areassavanna
climate type
SaharaDesert
climate
type
Animation
Explanation of ITCZ
The ITCZ is the meeting point of a hot, wet and unstable tropical
maritime air mass (mT) from the Gulf of Guinea (south east trade winds)
and a hot, dry and stable tropical continental (cT) air mass from the
Sahara desert (north east trade winds) also known as the Harmattan
winds. Where the air masses meet warm air rises, condenses and
causes heavy rain.
The meeting point of these two air masses moves north when the sun
moves north of the equator (June) and it moves south when the sun is
overhead south of the equator (December) because of the tilt in the
earth’s axis. It is known as the thermal equator.
In June the hot, moist mT air mass pushes north against the hot, dry cT
air mass. The rain reaches its furthest point north and the south has a
dry season.
In December the cT air mass pushes south and the north has a very dry
season.
Describe the rainfall graph for Gao which is in the south of the Sahara desert.
1. When is the maximum rainfall – amount and month?
2. When is there least rainfall – amount and month?
3. Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain
time of year?
Describe the rainfall graph for Bobo-Dioulasso which is in the Savanna region.
1. When is the maximum rainfall – amount and month?
2. When is there least rainfall – amount and month?
3. Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain
time of year?
Describe the rainfall graph for Abidjan which is on the Gulf of Guinea.
1. When is the maximum rainfall – amount and month? Is there just one peak?
2. When is there least rainfall – amount and month?
3. Write a sentence for the trend in rainfall. Is there a lot, does it fall at a certain
time of year?
Past Paper Question
“Tropical latitudes receive more solar energy than polar
latitudes. The atmosphere and oceans help to redistribute this
energy to maintain a global energy balance.”
Explain fully the ways in which the circulation cells in the
atmosphere help to redistribute energy (4 marks)
• At the Equator warm air rises and travels to the poles. The air cools and
begins to fall 30ºN and S of the Equator. Cooled air returns to the Equator.
This is the Hadley cell.
• Cold, dense air sinks at the poles and moves towards the Equator. At
about 60ºN and 60 ºS, the cold polar air begins to warm. This warm air
rises and returns to the pole, carrying heat energy. This is called the Polar
cell.
• The Ferrel Cell is caused by friction between the other two cells. The
Hadley Cell draws cool air down at 30ºN and S and the Polar Cell sends
warm air up at 60ºN and S.
• The three cells transfer heat energy from the Equator towards the Poles.
Assess out of 4. A maximum of 1 mark should be awarded for
correctly located or drawn Cells – with a maximum of 2 for the
explanation of any one cell.
A fully annotated diagram could score full marks. 4 marks
Attempt the 2011 Higher
atmosphere question.
Remember it is a 6 mark
answer not 12 marks.