Global Circulation of Air

Hellos! Today, we learnt more about the global circulation of air. (OK, sorry, there will be no diagrams)

The global model consists of the tropical cell (Hadley cell), the mid-lattitude cell (Ferrel cell) and the Polar cell.

The Hadley Cell
The Hadley cell is the in the area of zero degrees and thirty degrees north as well as zero degrees and thirty degrees south. What happens at the Hadley cell is that warm air rises and moves away from the earth and the air cools to the temperature of surrounding air. The air movement is unstable and there is convection rain. At the equator, due to insoluation from the sun - the intensity of heat received along the equator is high, the air rises. This air is warm air at low pressure.

The Ferrel Cell
The Ferrel cell is from thirty degrees north to sixty degrees north or thirty degrees south to sixty degrees south. At the Ferrel cell, the cold air (from Polar and sub-Polar regions) sinks and the decending air warms by compression, resulting in cloudless and stable conditions. At thirty degrees north/south, there is high pressure so the air seems to 'come in' as opposed to 'rise away' like at zero degrees.

The Polar cell
The Polar cell ranges from sixty degrees north to nienty degrees north or sixty degrees south to ninety degrees south. At the Polar cell, around the sixty degree north/south area, warm air from the tropics meets cold air from the Polar areas. The warm air rises quickly and compes into contact with the cold parcels of air. This results in instability and depressions. The cold air sinks at ninety degrees north/south and is at high pressure, resulting in dry and stable conditions at nienty degrees north/south.

Air moves from areas of higher pressure to lower pressure, however the air movement is not straight. Why is this so? This is due to the movement of the earth - remember the Coriolis Effect? On top of that, the land mass distribution is uneven, with more land in the Northern Hemisphere. This results in a differential temperature since land absorbs and gives out more heat than water. So what about monsoon winds? The cross over oceans and carry moisture. What path do they take?

Don't forget to read the notes! Especially on the Surface Features of the Global Atmospheric Circulation System (because I didn't write anything about that since it is there...)

<3 Huiling XD (10)