Wind is the movement of air molecules. There are two central concepts for understanding the cause of wind: air and air pressure.
8.4.2006
By: Matt Collins, Scientific American
Chris Weiss, professor of atmospheric science at Texas Tech University, provides this answer:
Simply put, wind is the movement of air molecules. There are two central concepts for understanding the cause of wind: air and air pressure.
The air contains nitrogen molecules (about 78% of the volume), oxygen (about 21%), water vapor and other gases in small quantities. All these air molecules move at high speed in every direction and are constantly colliding with each other and with bodies on the surface of the ground.
Air pressure is defined as the amount of force that these molecules exert on a given area. In general, the more air molecules there are, the greater the air pressure. The wind is driven by a force caused by a gradual change in pressure.
Changes in air pressure, such as those caused by the dynamics of storm systems or uneven heating of the sun in a given horizontal area, push air molecules from an area of relatively high air pressure toward an area of low pressure.
The high and low pressure areas shown on weather maps mainly cause the gentle breezes we usually experience. The pressure differences that cause such a wind do not exceed about one percent of the atmospheric pressure, and they are spread over the territories of entire countries. In contrast, the winds in strong storms originate from large areas where the pressure changes are much more significant.
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