Global Atmospheric Circulation
Without solar energy the air around the earth would remain still
At the equator, sunlight hits the surface directly
At the poles, sunlight hits the surface at an angle
Causes less heating
Light is spread over a greater area
More sunlight is reflected from the oceans and ice
1kW per square meter
0.5 kW per square meter
Sunlight warms the earth's surface
Radiates infrared radiation into the atmosphere
Some of this radiation is absorbed by greenhouse gasses, causing the atmosphere to warm
Water vapour
Carbon Dioxide
Methane
Other green house gasses
Warm air is lighter and rises
Cold air is heavier and sinks
Different parts of the earth's surface are travelling at different speeds
Forms a high pressure cell
Forms a low pressure cell
Due to the earth's rotation, wind does not move in a straight line
Due to inertia, winds blowing from the poles are deflected
The hot air rising from the equator is pushed towards the poles
They end up spinning around the polar regions
0º (on the equator), the surface travels at 1600 km/h
30º from the equator, the surface travels at 1400 km/h
60º from the equator, the surface travels at 800 km/h
90º from the equator (at the poles), the surface is stationary and does not move
Cells
Hadley Cell
(0º to 30º)
Polar Cell
(60º to 90º)
Air flows towards the faster traveling equator but drops behind because it is slower than the surface it is moving towards
Subtropical Jet
(30º, high pressure belt)
When the air from the equator is pushed towards a region where the earth is slower, the air will overtake the surface and will end up heading east
Air is diverted north and south
Polar Front
(60º, low pressure belt)
Westerly winds meet the cold polar easterly winds at a collision zone
Warm, moist, westerly air rises above the cold polar air
This produces a belt of storms
Inter Tropical Convergence Zone
(0º, low pressure belt)
Where the north east and south east trade winds meet
Ferrel Cell
(30º to 60º)
Air moving from high to low pressure systems is deflected by the Coriolis effect