1. Global Atmospheric Circulation
Revision Clock……
What is wind?
What is high and low pressure system?
Hadley cell
Ferrel cell
Polar cell
Climatic zones around the World
Climatic zones around the World continued
Extreme weather - wind
Extreme weather - temperature
Extreme weather - precipitation
Comparison of extreme weather – Australia & UK
Comparison of extreme weather – Australia & UK continued

2. Global Atmospheric Circulation
What is wind? Large scale movements of air caused by differences in air pressure. Differences in air pressure is caused by differences in temperature. What is a high and low pressure system? Warm rising air creates low pressure Cool falling air creates high pressure.

3. High
Low
High
Low
High
Low
High

4. Hadley Cell Ferrel Cell Polar Cell Where?
The equator to 30° north and 30° south
What happens?
Trade winds blow from the tropical regions towards the equator from a easterly direction.
Near the equator the trade winds meet and this warm air rises and forms thunderstorms
The air continues to rise until cools and sinks over subtropical regions
30° to 60° north and south of the equator
The cool air reaches the ground surface and moves towards the poles (westerlies)
The warmer surface winds meet colder air from the poles
The warmer air is less dense than the cold air so it rises, creating low pressure.
The air continues to move towards the poles
60° to 90° north and south of the equator
The cold air sinks creating high pressure. The high pressure air is then draw back towards the equator as surface winds

5. Climate zones around the World
The pressure belts caused by global atmospheric circulation cause variations to climate.

6. Temperate Climate
No extremes
Two air systems meet, one warm from the Ferrel and one cold from the Polar.
As a result low pressure is created to form clouds and frequent rainfall.
Arid (dry)
Hot climate with limited rainfall
High pressure system as two cells (Hadley and Ferrel) meet with sinking air preventing rainfall.
Polar Climate
Cold climate with limited rainfall
Temperatures are low all year round
High pressure from the Polar cell causes dry icy winds caused by the spin of the earth
Tropical Climate
Hot climate – with a wet and dry season
Low pressure system as a result of rising air by the equator. Temperatures are hot all the time and rainfall is high.

7. Extreme Weather Wind Temperature Precipitation Trade winds
Winds that blow from high to low pressure
Katabatic winds
Air flowing down hill
Jet streams
Winds high in the atmosphere
Tornadoes and tropical storms
Strong rotating winds
Albedo effect
How much a surface reflects or absorbs the suns rays
Cloud cover
Thick clouds reduce the temperature
Winds
Surface winds move heat around the world
Ocean currents
Ocean currents move heat easily
Land and sea
Although water is slower to warm up than land, it stays warmer for longer
Altitude
Higher up, air pressure is lower, which makes temperatures colder
Convection rainfall
Warm air rises and cools and condenses to form clouds.
When rain falls it can sometimes be heavy. Significant at the equator
Frontal rainfall
When warm air meets cold air, it is called a front. The warm air rises and forms clouds. Steady rainfall.
Relief rainfall
When wind reaches mountains, the warm air is forced to rise. Precipitation on the windward side of the mountain. As air descends on the leeward side it will be dry creating a fain shadow.

8. Extreme weather in two contrasting countries
Temperature
Precipitation
Wind UK
Australia

9. High
Low
High
Low
High
Low
High

10. Extreme weather in two contrasting countries
Temperature
Precipitation
Wind UK
Australia