1. Lesley Monk Balfron High School Session 2005/6
ATMOSPHERE
Lesley Monk
Balfron High School
Session 2005/6

2. THE THREE CELL MODEL;-FORMATION OF THE HADLEY CELL (1)
ATMOSPHERE
CELLS AND HEAT TRANSFER
A single cell model like in diagram 9 is too simplistic- we can find three interlinked cells!
THE THREE CELL MODEL;-FORMATION OF THE HADLEY CELL (1)
Insolation in tropical areas causes warm air to rise and spread polewards, carrying heat energy.
SOLAR ENERY
INSOLATION
Nb; lots of new terms to learn!

3. FORMATION OF THE HADLEY CELL (2)
ATMOSPHERE
FORMATION OF THE HADLEY CELL (2)
Air cools and begins to fall at about 30ºN and 30ºS of Equator.
Cooled air returns to the Equator.
NORTHERN HADLEY CELL.
SOLAR ENERGY
Heat energy is therefore transferred from the Equator to sub-tropical latitudes.
SOUTHERN HADLEY CELL.

4. FORMATION OF THE POLAR CELL (1)
ATMOSPHERE
FORMATION OF THE POLAR CELL (1)
Intensely cold, dense air sinks at the poles, then blows as surface winds towards the Equator.

5. FORMATION OF THE POLAR CELL (2)
ATMOSPHERE
FORMATION OF THE POLAR CELL (2)
At about 60ºN and 60 ºS, the cold polar air is warmed in contact with the earth’s surface.
NORTHERN POLAR CELLS.
SOUTHERN POLAR CELLS.
This warmed air rises and returns polewards, carrying heat energy.
This circular motion is called the POLAR CELL.

6. FORMATION OF THE FERREL CELL
ATMOSPHERE
FORMATION OF THE FERREL CELL
Unlike the Hadley and Polar Cells, the Ferrel Cell is not driven by differences in heat energy.
The Ferrel Cell is caused by friction where air is in contact with the other two cells.
(The Hadley Cell drags air down at about 30ºN and S.
The Polar Cell causes an uplift at about 60ºN and S. )

7. THE THREE CELLS TOGETHER
ATMOSPHERE
Polar Cell
THE THREE CELLS TOGETHER
Ferrel Cell
Hadley Cell
Hadley Cell
Ferrel Cell
Polar Cell

8. ATMOSPHERE
It is well worth making sure that you can see the rising and falling pattern of these cells.
The next section uses this to work out wind directions on the surface of the earth.
There are handouts of the next few slides; use them and diagram 13 to answer the later questions on the screen.

9. ASSOCIATED PRESSURE BELTS
ATMOSPHERE
ASSOCIATED PRESSURE BELTS
HANDOUT
Rising air at the equator causes the equatorial belt of low pressure
Polar high pressure
Mid latitude low pressure
Descending air at about 30ºN and 30ºS causes the sub-tropical belt of high pressure
Sub-tropical high pressure
Equatorial low pressure
Rising air at about 60ºN and 60ºS causes a mid-latitude belt of low pressure
Sub-tropical high pressure
Mid latitude low pressure
Descending air at the poles causes the polar high pressure areas
Polar high pressure

10. ASSOCIATED SURFACE WIND PATTERNS
ATMOSPHERE
ASSOCIATED SURFACE WIND PATTERNS
COPY TEXT
Winds always blow from high pressure to low pressure.
They are deflected because of the Coriolis Force which come about because of the rotation of the earth. ( see later slide)
HANDOUT
Polar high pressure
Mid latitude low pressure
Sub-tropical high pressure
Winds in Northern Hemisphere are deflected to the right.
Equatorial low pressure
Winds in the southern hemisphere are deflected to the left.
Sub-tropical high pressure
Mid latitude low pressure
These wind belts shift seasonally. (See next section)
Polar high pressure

11. Answer these five questions fully in sentences.
ATMOSPHERE
Answer these five questions fully in sentences.
Q1. What kind of pressure has rising air?
Low pressure has rising air.
Q2. What kind of pressure has falling air?
High pressure has falling air.
Q3. Name two latitudes with rising air.
The Equator and 60 degrees N/S have rising air.
Q4. Name two latitudes with falling air.
30 degrees N/S and the Poles have falling air.

12. ATMOSPHERE
Q5. Explain the two factors that make the NE trade winds blow in the direction they do.
( You will need to be able to do this for any of the winds in diagram 13 !)
i) Air is flowing from a high pressure area at 30 degrees north towards a low pressure area at the Equator.
ii). The winds are being deflected by the Coriolis force/ effect to the right as the area is in the northern hemisphere.

13. Rossby waves and the Jet Stream
ATMOSPHERE
Rossby waves and the Jet Stream
Not far above our heads in the northern UK is where the Ferrel and Polar cells meet.
Here is where powerful waves of turbulence occur called Rossby waves.
This turbulence is mainly responsible for the series of depressions and anticyclones that happen over Britain.
Read about these on pages 10 and 11, then answer the questions on the next slide.

14. Q1. In what direction do Rossby waves flow in the northern hemisphere?
ATMOSPHERE
Q1. In what direction do Rossby waves flow in the northern hemisphere?
They flow towards the east in the northern hemisphere.
Q2. What is the name of the contact zone between the two cells?
A. It is called the Polar Front.
Q3. In what way is stage 4 like the formation of a river’s ox-bow lake ?
A. Loops of turbulence get cut- off and isolated from the main flow.

15. What happens when you set off in a plane to fly to somewhere?
ATMOSPHERE
Q4.In what way is the Ferrel cell thought to be less effective in atmospheric heat transfer?
A. It seems that winds and ocean currents transfer more heat than this weak atmospheric cell.
THE CORIOLIS FORCE.
What happens when you set off in a plane to fly to somewhere?
The earth turns beneath you, and you have to keep adjusting your direction ! Watch……….

16. Got the idea? Note the runners path is curved!
ATMOSPHERE
Destination
has moved
Direction of Earth-spin
Got the idea? Note the runners path is curved!
New direction
Destination
has moved
New direction
Thirty minutes in
Twenty minutes in
Destination
has moved
New direction
Ten minutes in
start
destination
Initial direction

17. Pages 14 and 15 are very technical !
ATMOSPHERE
Pages 14 and 15 are very technical !
The information is of the kind that can give extra marks in an extended answer.
Ignore it at your peril !
We suggest that you read it at home where you can think deeply about it !
You will need to have a basic understanding of why the wind belts are in different places at different times of the year.