1. Heat Transfer Due to Atmospheric Motion
Page 224 to 228

2. What causes wind?
Wind is the horizontal movement of air in the atmospheric system
Winds result from differences in air pressure
Differences in air pressure are caused by differences in temperature & gravity
E.g. pressure falls rapidly with height
Low pressure area
High pressure area
wind

3. Average pressure at sea level is 1013mb LOW v HIGH
Increased temperatures
Air heats & expands
Less dense & rises
Creates low pressure below
Drop in temperature
Air cools & contracts
More dense & sinks
Creates high pressure below

4. Draw 2 diagrams to show facts below
Blows inwards
Rising
Anticlockwise
Strong winds –steep pressure gradient
HIGH
Out-blowing
Descending
Clockwise
Gentle winds – gentle pressure gradient

5. Air movement on a rotation free earth
If earth did not rotate
If earth was entirely either land or water
There would be just one large cell
Wind would move directly from high to low pressure
HOW EVER EARTH IS NOT LIKE THIS

6. Tricellular Model 1686 – Halley – one cell
1735 – Hadley – expanded one cell theory
1856 – Ferrel – discovered three cells
1941 – Rossby – refined the 3 cell theory

7. Latent heat & moisture picked up from tropical oceans
Towering cumulonimbus clouds typical of equatorial climate
Mid-latitude depressions form
Horse latitudes – calm seas slowed sailors, no food for animals, dead horses thrown overboard
Doldrums – gentle, variable winds

9. Mid-latitude depressions at the polar front
Cumulonimbus clouds at ITCZ
Mid-latitude depressions at the polar front
Clear skies due to high pressure

10. The Coriolis Force It is a deflecting motion or force
Suggested by G.G. de Coriolis in 1835
Developed by W. Ferrel in 1855
The rotation of the earth causes a body moving across its surface to be deflected to the right in the N hemisphere and to the left in the S hemisphere

11. Coriolis Force 3 controls on wind: Pressure gradient Coriolis Force
Friction with land surface
Coriolis Force

12. - eastwards flights faster than westwards
ROSSBY WAVES = a belt of upper air westerlies which often follow a meandering path.
Evidence: pilots in WW 2 noticed:
- eastwards flights faster than westwards
- N-S flights often blown off course

13. Seasonal change in number of meanders – 4 to 6 in summer, 3 in winter

14. Their purpose is the rapid transfer of energy
Jet streams = narrow bands of extremely fast moving air found within the Rossby Waves
Their purpose is the rapid transfer of energy
Speeds can exceed 230km/hr
Can carry volcanic ash around earth in 1-2 weeks
5 recognised jet streams:
2 significant - POLAR FRONT JET STREAM
- SUBTROPICAL JET STREAM
1 seasonal – EASTERLY EQUATORIAL J.S.

15. Normal path of J.S. over Britain is to NE so frequent wet & windy weather as warm air moves north

16. Polar Front Jet Stream (divides Ferral & Polar cells)
Where J.S. moves south:
Cold air
Descends
Clockwise
Dry
Stable
High pressure
Anticyclones
Where J.S. moves north:
Warm air
Rises
Anticlockwise
Strong winds
Heavy rain
Low pressure
Depressions

17. SUBTROPICAL J.S.
25-30 degrees
Divides Hadley & Ferral Cells
Meanders less than PFJS
Lower wind velocities
Similar west to east path
EASTERLY EQUATORIAL J.S.
Seasonal
Associated with summer monsoons
Indian subcontinent
MONSOON = a seasonal reversal of wind direction in S.E. Asia

18. Balloon uses jet stream to orbit the earth