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

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.

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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

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

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.

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.

Extreme weather in two contrasting countries Temperature Precipitation Wind UK Australia

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Extreme weather in two contrasting countries Temperature Precipitation Wind UK Australia