Introduction to the Atmosphere
The Earth has an atmosphere which we commonly call air. Air contains oxygen for breathing, nitrogen and small amount of other gases, like the greenhouse gases which keep Earth naturally warm and suitable for life. The air also contains pollution. Some of this is natural, like dust from volcanoes, but a lot is now man-made, and comes from the burning of fuels for energy, electricity, heat and transportation.
The air also contains a lot of water in the form of moisture. When it rains we can see it. For the rest of the time, it is present in air in the form of invisible vapour or visible clouds, and is constantly recycled between the Earth and atmosphere by means of the water cycle. Moisture in the atmosphere is a cause of a lot of the world's weather.
Most air lies near the Earth's surface in the lowest layer of the atmosphere called the troposphere, pushed down by gravity. Most of the world's weather occurs in the troposphere which is only 10 km thick. The weather is caused by the movement of heat. Heat is exchanged between hot and cold places by moving air or wind, driven by differences in air temperature and pressure. The atmosphere extends a long way out towards space, and is made up of different layers. The stratosphere for example, lying above the troposphere, contains the ozone layer, which protects life on Earth from harmful ultraviolet rays from the Sun. Higher still, meteors burn up in the atmosphere, and can be seen as shooting stars at night.
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• ARIC
• US NOAA
• Chain Reaction
• AtmoSphere
• Introduction
• Air
• Air Layers
• Clouds
• Meteors
• Moisture
• Pollution
• Pressure
• Temperature
• Weather
• Wind