Wind

Wind is the natural movement of air or other gases relative to a planet's surface, ranging from brief gusts in a thunderstorm to steady global circulation patterns that span hemispheres. It is driven mainly by differences in atmospheric pressure, which themselves come from uneven heating of the surface, so air flows from higher pressure toward lower pressure. On a rotating planet such as Earth, the Coriolis effect bends this flow into large scale patterns, including the trade winds near the tropics, the westerlies of the mid latitudes, and the polar easterlies. Near the ground, friction slows the wind and pulls it inward toward low pressure areas, while local effects such as coastal sea and land breezes and mountain terrain produce their own smaller wind patterns.