2. Structure of the Atmosphere

It is the lower part of the atmosphere which has interested man from times immemorial. But from the beginning of the 20th century, when aeroplanes and radio waves were invented, the knowledge of the upper part of the atmosphere became rather essential. The earth’s atmosphere consists of zones or layers arranged like spherical shells according to altitude above earth’s surface. Each zone has a unique set of characteristics. For the most part the layers are

1 The stratospheric polar vortex is a large-scale region of air that is contained by a strong west-to-east jet stream that circles the polar region.

not at all sharply defined, and their boundaries are arbitrarily established. The density, temperature and composition of the atmosphere varies with altitude. Density is highest near the surface of the earth and decreases with increasing altitude. The temperature changes differently in different layers. Heavy gases such as Oxygen exist near the surface. At greater heights, the lightest gases do in fact separate out, forming several concentric gas envelopes around the Earth.

The atmosphere is divided into the five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere.