THE EARTH

The Earth's Atmosphere and its Importance for Life on Earth

The Earth's Atmosphere and its Importance for Life on Earth

The Structure of the Earth

The structure of the earth is made of five major layers namely:

Troposphere

Stratosphere

Mesosphere

Thermosphere and

Exosphere

Troposphere

The lowest layer of the atmosphere is the troposphere, where most weather takes place. And most thunderstorms don't raise much above the top of the troposphere, which is about 10 km. This layer's pressure as well as density quickly decreases with height, and at the same time temperature at a constant rate usually decreases with the height known as the lapse rate. For the troposphere the standard lapse rate is a decrease of about 6.5 degrees Celsius (C) per kilometre (km) it may be about 12 degrees F (Windley, 1976).

Tropopause and Isothermal

Troposphere is bounded above by a boundary called tropopause, which is marked as the point where the temperature does not decrease any more with height but becomes constant with it. Thus, any such layer in which the temperature remains constant with height is known isothermal.

Having an average height of about 10 km, which is higher in equatorial regions and lower in Polar Regions, the tropopause remains in contact to approximately 7 miles, or at about 200 mb (20.0 kPa) pressure level (Schopf, 1983).

Stratosphere

The next layer above the troposphere is the stratosphere. This layer is characterized mainly as a steady, stratified layer which has a throughout large temperature inversion. However, the major effect of this layer has on weather in the manner that its constant air prevents large storms from extending much beyond the tropopause (Windley, 1976).

Stratosphere

Now stratopause bounds the stratosphere, where the atmosphere once again becomes isothermal. The average height of the stratopause is about 50 km, or 31 miles and is approximately the 1 mb (0.1 kPa) pressure level.

Mesosphere

Over 99.9 percent of the atmosphere's mass lies below the mesosphere, this is the middle layer in the atmosphere. It has two basic points. Firstly, temperature decreases with height, where at the top of mesosphere, air temperature reaches its coldest value, which is around -90 degrees Celsius or -130 degrees Fahrenheit. Secondly, the air is tremendously thin at this level (Schopf, 1983).

Mesopause

The mesosphere is bounded above by the mesopause, which has an average height of approximately 85 km (53 miles). Here again the atmosphere becomes isothermal. This is approximately 0.005 mb (0.0005 kPa) pressure level (Schopf, 1983).

Thermosphere

The thermosphere is a warm layer, which has a significant temperature inversion. The few molecules present in the thermosphere receive special amounts of energy from the sun that causes the layer to warm. However, temperature on the other hand, is a measurement of the mean kinetic energy, or average speed of motion, of a molecule. Hence, only a few molecules are present, therefore, each has a large amount of kinetic energy.

Finally, came the exosphere, which is above the thermosphere. However, unlike the other layers there is no well-defined boundary between the thermosphere and the exosphere, which means that there is no boundary layer called the ...