Do First - Air Pressure Ideas

Air masses are large bodies of air that have uniform temperature, humidity, and pressure. Regardless of where they form, air masses can change as they move over Earth's surface, resulting in changes in weather.

Jet Streams were discovered during World War II, when American pilots flew their bombers higher than normal to avoid anti-aircraft fire. At those high altitudes, the jets speeds increased in some areas. The only logical explanation was the planes had entered a stream of swiftly moving air.

Jet streams "follow the sun" in that as the sun's elevation increases each day in the spring, the average latitude of the jet stream shifts poleward. (By Summer in the Northern Hemisphere, it is typically found near the U.S. Canadian border.) As Autumn approaches and the sun's elevation decreases, the jet stream's average latitude moves toward the equator.