WIND
The sun cannot heat the Earth evenly; therefore areas of warmer air and areas of cooler
air develop over different parts of the country. Because warm air is less dense than
cool air, it rises, letting the cool air move in to take its place. The warm air creates an
area of low pressure and the cold air creates an area of high pressure.
Wind can be defined as the horizontal movement of air from one place to another. Air
moves from areas of high pressure to areas of low pressure. If the difference in
pressure is small, the air movement is slight, and the wind is gentle. When the
difference in pressure is great, the air movement is rapid or fast and the wind is strong.
In the United States, winds generally blow from the west coast towards the east coast.
Weather systems move along with the winds, from the west to the east.
In the stratosphere, there are strong winds that flow from the west towards the east.
This system of winds is known as the jet stream. The winds within the jet stream vary
greatly in speed. They may blow anywhere from 129 miles per hour to 966 miles per
hour. Jet stream winds are strong enough to slow down planes heading west across
the U.S. by as much as 161 mph. These same winds can help speed up planes
heading east, allowing them to conserve fuel.
1. Which type of air is more dense, warm air or cool air? ______________________
2. Which type of air rises because it is less dense, warm or cool air? _____________
3. What is wind?
4. In which direction do weather systems move? Why do they move in this direction?
5. Wind moves from an area of _____________________ pressure to an area of
___________________ pressure.
6. If the difference in pressure is great, is the wind strong or light? _____________
7. In what part of the atmosphere is the jet stream found? ______________________
8. In which direction does the jet stream move? _____________________________
9. Why are airplanes heading west slowed by the jet stream?
10. Why do different temperatures of air develop at different parts of the country?