Wind

Wind Air in motion. Winds are caused basically by temperature differences over the Earth's surface. A major circulation pattern is set up as air over the equator becomes hot and rises. This creates a low-pressure region, known to early sailors as the doldrums, where the air is still and waters calm for days on and.

As the hot air rises, cool air from polar regions moves in to take its place. The hot air in turn cools and sinks down near the poles. if the earth were not rotating, the winds would blow north-south. But the Earth is rotating, and the winds are deflected by the so-called Coriolis affect. This makes the winds blow towards the equator from the north-east in the northern hemisphere and from the south-east in the southern.

such winds, called the trade winds, blow towards the equator from about the 30th parallels north and south. Between about the 30-60th parallels, by contrast, the winds blow predominantly from the west-from the south-west in the northern hemisphere and from the north-west in the southern. These winds are called the prevailing westerlies.