1. Air pressure is caused by the weight of air above and is highest at sea level, measured with a barometer. Wind is caused by differences in air pressure between areas of high and low pressure. 2. Low pressure systems, or cyclones, have decreasing pressure towards the center and cause inward winds and rising air, bringing clouds and precipitation. High pressure systems, or anticyclones, have increasing pressure towards the center and cause outward winds and sinking, clear air. 3. Global wind patterns are affected by uneven solar heating between the equator and poles, forming convection cells, and between land and sea surfaces, such as monsoon winds caused by seasonal offshore and onshore breezes.

1. AIR PRESSURE AND WIND

3. BAROMETERS

28. U.S. Pattern: La Niña events are characterized by drier than normal conditions across the southern U.S. stretching from California to Florida and up into the mid Great Plains and Midwest. And La Niña events are characterized by colder than normal temperatures from California to Washington State and across the northern tier of state to Minnesota and Wisconsin.