In Motion Weather 101 Wind is literally air in motion. Because air is free to move, it very readily reacts to forces exerted upon it. The primary driving force for the wind is a difference in atmospheric pressure along a horizontal surface.
Atmospheric pressure is the weight of the column of air above an area on the surface.
The result is that on the surface there are areas of high and low pressure. For example in Illustration A, a column of air which is cold and dense results in higher pressure at the surface than where a column of the same depth is filled with warmer and thus less dense air. These cold high pressure systems develop, not surprisingly in the polar or arctic regions and are called polar highs or arctic highs. Higher pressure can also result if the column is higher in one region than another. This piling on of air as shown in Illustration B, occurs in the sub-tropics in both hemisphere.