Wind, in climatology, the movement of air relative to the surface of the Earth. Winds play a significant role in determining and controlling climate and weather. A brief treatment of winds follows.

Wind occurs because of horizontal and vertical differences (gradients) in atmospheric pressure. Accordingly, the distribution of winds is closely related to that of pressure. Near the Earth’s surface, winds generally flow around regions of relatively low and high pressure—cyclones and anticyclones, respectively. They rotate counterclockwise around lows in the Northern Hemisphere and clockwise around those in the Southern Hemisphere. Similarly, wind systems rotate around the centers of highs in the opposite direction.

In the middle and upper troposphere, the pressure systems are organized in a sequence of high-pressure ridges and low-pressure troughs, rather than in the closed, roughly circular systems nearer the surface of the Earth. They have a wavelike motion and interact to form a rather complex series of ridges and troughs. The largest of the wave patterns are the so-called standing waves that have three or four ridges and a corresponding number of troughs in a broad band in middle latitudes of the Northern Hemisphere. The westerlies of the Southern Hemisphere are much less strongly affected by standing disturbances. Associated with these long standing waves are the short waves (several hundred kilometers in wavelength) called traveling waves.

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