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A. Why Do They Exist?
Infrared satellite image of North America
Our spinning planet is covered with moving air. Some of this air is over the ocean and some is over the land. The ground gets warm faster than water, but also gets cold faster than water. That is why it is normally colder over land in the winter, and warmer over land in the summer. When the ocean is warmed by the sun, the water absorbs heat and warms the air above it.
At the same time, the land can become cold and cool the air above it. Because of heating and cooling, air can move up and down. When a pocket of air gets too warm, it rises until it is the same temperature as the surrounding air. Just the opposite happens when a pocket of air gets cooled, it sinks. The combination of warm and cold areas, and rising and sinking air results in what we call weather systems.
B. How Do They Move?
Areas of high pressure, called Highs, have air that sinks. This air tends to be cold and produces clear skies and fair weather. Areas of low pressure, called Lows, have warm air that rises. They can cause clouds to form, rain to fall, and storms to occur. Weather systems in the United States and within the mid-latitudes, between 30° N and 60° N and between 30° S and 60° S, usually move from West to East. Weather systems in other latitudes move from East to West.
C. How Does Weather Affect You?
Think about how the weather affects your life. Draw pictures of the clothes you would have to wear if the following weather were to happen. What do you wear when it...
- ...rains?
- ...snows?
- ...is hot?
