A current of air, especially a natural one that moves along or parallel to the ground, moving from an area of high pressure to an area of low pressure. Surface wind is measured by anemometers or its effect on objects, such as trees. The large-scale pattern of winds on Earth is governed primarily by differences in the net solar radiation received at the Earth's surface, but it is also influenced by the Earth's rotation, by the distribution of continents and oceans, by ocean currents, and by topography. On a local scale, the differences in rate of heating and cooling of land versus bodies of water greatly affect wind formation. Prevailing global winds are classified into three major belts in the Northern Hemisphere and three corresponding belts in the Southern Hemisphere. The
trade winds blow generally east to west toward a low-pressure zone at the equator throughout the region from 30° north to 30° south of the equator. The
westerlies blow from west to east in the temperate mid-latitude regions (from 30° to 60° north and south of the equator), and the polar
easterlies blow from east to west out of high-pressure areas in the polar regions. See also
Beaufort scale, chinook, foehn, monsoon, Santa Ana.
wind
Global wind patterns are determined by differences in atmospheric pressure resulting from the uneven heating of the Earth's surface by the Sun. As air is heated along the equator it rises, creating a zone of low pressure that draws air toward it throughout the tropics and produces the surface flow known as the trade winds. After it rises, the warm equatorial air flows north and south, cooling in the upper atmosphere until it is dense enough to descend near the Tropics of Cancer and Capricorn. Part of this cooler air flows at surface level toward the poles, where it meets the colder, drier air flowing away from the poles. The Coriolis effect deflects these broad surface flows, turning winds that blow toward the equator into easterlies and those that blow toward the poles into westerlies.
