From a general point of view, the atmospheres composition seems simple. It contains oxygen produced mostly by algae and other plants. Statistically speaking, it is composed of 79% nitrogen, 20% oxygen and 0.036% carbon dioxide. The rest is made up of small amounts of other gases. The atmosphere is divided into four layers. The atmosphere also has a layer of ozone.
The layers of the atmosphere listed from lowest altitude to highest altitude are the troposphere, stratosphere, mesosphere and thermosphere. The troposphere extends from the Earths surface up to about 14 kilometers in altitude. All human activities occur in the troposphere. The troposphere is the layer where all weather we experience takes place. It is a thin layer of the atmosphere. The warmest part of the troposphere is at the bottom. Commonly in the troposphere, altitude increases as temperature decreases. However there is an exception. Depending on wind currents, mountain ranges can cause lower troposphere areas to have an opposite effect.
The next layer is called the stratosphere. There are gradual changes from the troposphere to the stratosphere. The stratosphere starts at about 11 km in altitude. Here, the air flows mostly sideways. Most commercial aircraft travel takes place in the lower part of the stratosphere. Extremely high and wispy clouds can form in the lower stratosphere; however no major weather formations can take place in the stratosphere. In this layer, temperature increases as altitude increases.
The third layer of the Earths atmosphere is the mesosphere. This layer extends from 50 to about 80-90 km in altitude. Temperatures in the upper mesosphere fall as low as -100°C. The temperature varies in this layer by latitude and season. Temperature decreases with altitude in the mesosphere. The mesosphere is commonly known as the middle layer.
The last and uppermost layer of the atmosphere is the thermosphere. In this layer, temperatures can reach an outstanding high of 1982 degrees celcius! Extreme thermosphere temperatures are a result of UV radiation absorbtion. Radio waves bounce off the thermosphere. The aurora is found in the thermosphere. The Aurora Borealis and Aurora Australis are the northern and southern lights. They cause magnetic storms near the polls.
The ozone layer is concentrated in a thin layer located at the uppermost part of the stratosphere, approximately 15-30 km above the Earths surface. Ozone is an exceptionally reactive form of oxygen. The roll of the ozone layer is to protect the Earth from the harmful effects of ultra violet radiation. To complete its role, ozone needs atmospheric oxygen. Ultra violet radiation is bad because it causes breaks in the human bodys nuclear proteins leaving opportunity for cancers and other health issues to take place. U.V. radiation also has bad effects on some crops, materials and marine organisms. Ozone is much less widespread than normal oxygen. The formation of the ozone layer is a tricky matter. Out of every 10 million molecules, about 2 million are regular oxygen.
Another important topic on the atmosphere is atmospheric pressure. Air pressure is defined as the gravimetric force applied on you by the weight of air molecules. The Earths atmosphere presses down on every surface with a force of 1kg/cm2. This means that the force on 1000 square centimeters would be nearly a ton! Weather scientists measure air pressure with a barometer. Air pressure effects weather in the sense that if there is high air pressure, there will be cooler temperatures and sunny skies. If there is low air pressure system, there will be warmer temperatures and possibly thunder storms.
The atmosphere is extremely vital to Earth. Without it, the Earth would be unprotected from UV radiation and there would be no persistent climate and weather patterns. It is our jobs as humans to do what we can to protect the atmosphere.
The book I used was.
Earth Science Demystified by Linda Williams. Published by Mc Graw Hill. 2004