Wind and atmospheric circulation
Wind is the movement of air across the surface of the Earth, and it is one of the basic elements of weather and climate. Air moves because the atmosphere is not heated evenly: the Sun warms some areas more than others, creating differences in temperature and therefore in air pressure. Air flows from regions of higher barometric pressure toward regions of lower pressure, and this flow is what is felt as wind. The greater the pressure difference over a given distance, the stronger the wind.
The path of moving air is not straight. Because the Earth rotates, winds are deflected through the Coriolis effect — to the right in the Northern Hemisphere and to the left in the Southern. High in the atmosphere, where surface friction is slight, the balance between the pressure difference and the Coriolis deflection produces what is called the geostrophic wind, which flows roughly parallel to lines of equal pressure. Near the ground, friction slows the air and alters its direction. These influences combine to create the great wind belts of the planet, such as the trade winds and the prevailing westerlies.
On a smaller scale, local winds arise from local temperature contrasts. Sea and land breezes, for example, develop along coasts because water and land warm and cool at different rates, reversing direction between day and night. Animations and simulations are often used to illustrate these processes, showing how pressure differences and the rotating Earth together govern the winds.
Frequently asked questions
- What causes wind?
- Uneven heating of the Earth creates differences in air pressure, and air flowing from higher to lower pressure is what we experience as wind.
- How does the Earth's rotation affect wind?
- Through the Coriolis effect, the rotation deflects moving air — rightward in the Northern Hemisphere and leftward in the Southern — shaping global wind patterns.
- Why do sea breezes form?
- Land and sea heat and cool at different rates, so during the day cooler air over the sea flows toward the warmer land, with the flow reversing at night.
