•Warm air rises in the tropics when it is heated by the sun; air from the
tropics receives the greatest solar energy input. This rising air is replaced by air
that flows in toward the equator from the north and south.
•Intertropical convergence zone – the tropical region where the air rises
most strongly; moves north and south with the passage of the sun overhead.
•Cool air can`t hold as much moisture as warm air, so heavy rains fall in the
intertropical convergence zone as the rising air cools and releases its moisture.
•At the poles, where there is little solar energy input, air descends. These
movements of the air masses are largely responsible for global wind patterns.
•Spinning of the earth on its axis also influences surface winds because
earth`s velocity is rapid at the equator, where its diameter is greatest, but
relatively slow close to the poles.
•As an air mass moves toward equator, it confronts an increasingly faster spin,
and its rotational movements are slower than that of earth beneath it.
•As an mass moves pole ward, it confronts an increasingly slower spin, and it
speeds up relative to earth beneath it.
•Air masses moving latitudinally are deflected to the right in the Northern
Hemisphere, and to the left in the Southern Hemisphere.
•Air masses moving toward equator from north and south veer to become the
westerly winds that prevail at mind-latitudes.
•When air masses are brought into contact with a mountain range, the air
rises to pass over the mountains, cooling as it does so. Therefore clouds
frequently form on the windward side of the mountains (side facing into the
winds) and release moisture as rain or snow. On leeward side (opposite from
direction of winds) of mountains, the now-dry air descends, warms and once
again picks up moisture.
•Rainshadow – the relatively dry area on the leeward side of a mountain