Wind

1. Wind Concept: winds are produced by the uneven heating of Earth’s surface and the resulting rise and fall of differentially heated air masses.

2. Wind-Definition and mechanism • Wind is air in motion; • It is a result of the uneven heating of the earth’s surface by the sun; • As the sun warms the earth’s surface. The atmosphere warms too… warm air rises, then cool air moves in and replaces the rising warm air; • This movement of air is what makes the wind blow.

3. High and low pressure systems • Wind blows because it has weight; • Wind blows from areas of high pressure to areas of low pressure;; • Cold air weights more than warm air so the pressure of cold air is greater (think: the more weight, the more pressure); • High pressure: Thumb up, beautiful weather; • Low pressure: thumb down, fair, nice weather

4. Local Winds • Cooler moist air from over the water slides beneath the rising air, creating a sea breeze on an ocean beach; • At night the water stays warm after the land has cooled, resulting in an offshore breeze.

5. Global Winds • In general, warm, tropical air tends to float toward the cool poles, while polar air slides toward the equator; • Earth’s air masses break up into cells that result in certain consistent wind patterns.

6. Global Winds • Doldrums=mostly very calm air in a band over the equator; • Trade winds=warm, steady winds blow back toward the equator in usually clear skies; • Prevailing westerlies=cool air, usually moving quickly toward the poles from west to east in both hemispheres; • Polar easterlies=cold, fairly weak winds blowing from east to west.