Download global circulation

GLOBAL CIRCULATION
The greatest amounts of solar radiation, over a year, are received at the equator. Solar radiation is
concentrated here and the sun is always at a high angle. At the equator there is a net radiation gain:
more radiation is received than is eventually lost from the atmosphere. At the poles there is a net
radiation loss: less radiation is received than is eventually lost from the atmosphere.
Because the equator is not continually warming up and the poles are not cooling down, then there
must be some kind of mechanism that transfers excess energy from the equator towards the poles.
One mechanism is the global circulation. (Ocean currents and weather systems also transfer energy)
The diagram you are about to draw is a very simplified version of that circulation.
At the equator heating of the ground causes air to rise by conduction and then convection.
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Draw an arrow to represent the rising air over the equator.
At the ground surface write an L or an H to represent the pressure that would be experienced
at the ground.
At the tropopause the inversion in the stratosphere puts a ‘cap’ on rising air. Air moves northwards and
southwards at this height. Cooling and the Coriolis effect force the air downwards at 30N and 30S.
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Draw arrows to represent the air moving out and then downwards in both hemispheres.
At the ground surface write an L or an H to represent the pressure that would be experienced
at the ground at 30N and 30S.
Some of the air that sinks at 30N and 30S moves back towards the equator, over the surface. Some of
the air moves northwards and southwards towards 55N and 55S.
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Draw arrows across the surface to show these horizontal movements.
Air sinks over the two poles.
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Draw arrows to represent the sinking air here.
At the ground surface write an L or an H to represent the pressure that would be experienced
at the ground at the poles.
Cold air moves out over the surface from the two poles towards 55N and 55S.
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Draw arrows to represent this movement
You will see that at 55N and 55S there is a meeting of cold polar air and warm tropical air. The two air
masses do not mix. The point of meeting is called a front. The warm air rises at these latitudes along the
‘front’.
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Draw arrows to represent the warm air rising at 55N and 55S.
At the ground surface write an L or an H to represent the pressure that would be experienced
at the ground at 55N and 55S.
Some of this rising air will move northwards at height towards the poles.
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Draw arrows to represent this movement.
Now … deflect the winds in the northern hemisphere to their right… and the winds in the
southern hemisphere to their left… (to show the coriolis effect)