Some air movements are the result of the systematic pressure gradients that arise from latitudinal changes in the Earth’s surface temperature. One notable example is the Hadley Cell, a movement of warm air from the tropics that rises, flows toward the poles and then cools and sinks at around 30 degrees north and south of the equator. This movement creates belts of low pressure in the tropics and high pressure in the temperate zone where the air sinks.
Air flowing from zones of high pressure to zones of low pressure causes winds, just like the way air gushes from a punctured tire or balloon. Uneven heating and convection generate the pressure differences; the same tendencies create currents in a saucepan of water heating on a stove. The difference in this case is that the convection currents that create winds take place on a far greater scale.
Because both small winds and larger pressure belts are driven by temperature differentials, changes in temperature at the surface can alter them. For example, ENSO (southern oscillation) events, such as El Nino and La Nina, include unseasonal alterations in ocean temperature that can magnify or decrease the strength of wind belts across the globe. Similarly, when centers of low pressure or high pressure move through an area, they can alter the flow of local wind and even create storms. Tropical cyclones come from low pressure zones in the tropics, and their powerful winds are some of the strongest on the planet.
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