Prevailing Winds

What is wind? Wind is a movement of air in the atmosphere. Some winds are local or regional meaning they cover a fairly small area Winds that affect large areas are called prevailing winds. They affect weather around the world.

The Coriolis Affect http://www.youtube.com/watch?v=mcPs_OdQOYU The appearance of changing direction of winds in the upper atmosphere

Solar Heating and Wind Solar energy strikes most directly near the equator. The warm air rises and expands leaving behind an area of low pressure. When the warmed air reaches the tropopause it moves northward. It eventually becomes cold and more dense around 30º latitude and begins to sink creating an area of high pressure. Air at the surface moves from this high pressure area the low pressure near the equator. The air twists to the right from the coriolis effect causing the northeast trade winds.

Pressure and Wind When the sun warms the air, the air expands, gets lighter, and rises.  Cooler, heavier air blows to where the warmer and lighter air was wind usually blows from areas of high air pressure to areas of low pressure. If the high pressure area is very close to the low pressure area, or if the pressure difference (or temperature difference) is very great, the wind can blow very fast.

Jet Streams The major jet streams on Earth are westerly winds (flowing west to east). Jet streams form near boundaries of adjacent air masses with significant differences in temperature, such as the polar region and the warmer air towards the equator

Jet streams The strongest jet streams are the polar jets, at around 7-12 km (23,000-39,000 ft) above sea level, and the higher and somewhat weaker subtropical jets at around 10-16 km (33,000-52,000 ft). The northern hemisphere and the southern hemisphere each have both a polar jet and a subtropical jet.

Effects of Prevailing Winds Distribute large amounts of solar energy across the world Cause a variety of precipitation such as snow and rain At the 30º where the cold dry air descends deserts form