Who can explain "Atmospheric circulation"?

Question

http://en.wikipedia.org/wiki/atmospheric...

IN THIS WEBSITE THEY HAVE THE PICTURE OF THE EARTH WITH A BUNCH OF ARROWS ALL OVER THE PLACE, CAN YOU EXPLAIN TO ME WHAT THESE ARROWS ARE DOING OR SHOWING?

Answer 1

Maximum solar radiation is received in the equator regions and minimum in the polar regions.A temperature gradient resulting in a pressure gradient(high pressure over poles and low pressure over the equator)is created from the equator to poles.If the earth's surface were uniform and the earth were non-rotating,a flow of air from the poles towards the equator at surface levels and a reverse flow at a higher level will be noticed due the above temperature gradient.But the above circulation breaks into three cells due to the rotation of the earth. The reason is given below.
Because of the rotation of the earth , the air moving towars higher latitudes will become westerly and gain in speed and the air moving towards the equator will become easterly and will have increased speeds.Since wind speed cannot increase beyond certain limits,the single circulation above mentioned breaks into three circulations.Two direct circulations,one in the tropics and another in the polar regions in each hemisphere and a third reverse circulation in the middle latitudes.In conformity with the above wind circulation, low pressure belts exit on the equator and about 60 degrees latitude.There are high pressure belts near about 30 degrees latitudes and at the poles.In conformity with this pressure field, easterly winds prevail in the tropical regions and near the polar regions whereas westerlys prevail over temperate zones . The wind given above are at ground level and it will be opposite in the higher level in all the three cells.

Answer 2

Good question. I think I can help you understand this model a little better. What governs the motion of the atmosphere is a combination of the Sun's radiation on the Earth, the Earth's orbit, and its inclination to its orbit. While the equator receives roughly equal solar radiation throughout the year, the poles receive varying amounts. This results in global convection currents such as the Hadley current which consists of rising air in the warmer tropics and descending air over the mid-latitudes and over the poles. Sinking air from the polar region then flows south the leading edge of which is referred to as the polar front. Diagrams of these flows are normally shown with arrows with maybe one color for the surface level winds and another color for the upper level winds. I hope this helps you a little more.