Dear students,

We continue studying the layers of the Earth’s atmosphere.

The weather layer. The most impor­tant layer of air for people on the earth is the one immediately above the earth's surface. This is the troposphere, or weather layer. Like all of the other layers of the atmosphere, it is widest at the equator and narrowest at the poles. Practically all of the atmosphere's oxy­gen and all of its water vapor are found in the weather layer.

Air in the weather layer is denser than air in the other layers. The air is densest near the earth's surface. As altitude increases, the air gradually thins. At altitudes above 10,000 feet (3,000 m), people who are not used to the thinner air of higher altitudes find breathing more difficult.

The conditions of the air in the tropo­sphere change very often. These chang­es are what make weather. You will learn more about these changes and why they take place further. Just remember that all weather changes take place in the tropo­sphere—the earth's weather layer.

The air-travel layer. The upper reaches of the troposphere gradually merge into the stratosphere about 10 miles (16 km) above the earth's surface. The air in this layer is clearer and much thinner than air in the weather layer. Because it is free of water vapor, the stratosphere has no clouds. It is also free of strong up and down movements of air. For these reasons, jet planes use it for long distance air travel.

The stratosphere is important for an­other reason. It contains ozone, a special form of oxygen. Ozone protects the earth by blocking out many of the most dam­aging of the sun's rays. Without the ozone in this layer, much of the life on earth would disappear in a matter of minutes.

The radio layer. Radio waves travel in straight lines. They travel only a short distance before the earth curves away beneath them. Without the charged particles called ions in the ionosphere, radio waves would travel far into space and never be received on the ground. But the radio waves hit the ions, which reflect the radio waves back toward the earth, where they can be received hundreds, even thousands, of miles from their sending points.

 

Name

For today you need to answer the following questions:

Why is the troposphere important to people on the earth?

In what layer of the atmosphere is air the densest?
The thinnest?

Why do jet planes often travel in the stratosphere?

What is ozone?
How does it protect the earth?

What are ions?
Where are thy found in the atmosphere?
How do they make long distance radio communication possible?

 I’m looking forward the letters from you,

Mrs. Nicolaev