The Layers of the Atmosphere

The Weight of Air

As you stand on the surface of the Earth, your body bears the weight of a column of air that stretches upwards for several hundred kilometers. The weight of this air column pushes equally on every square inch of your body exerting a pressure in every direction. This pressure results from the constant collisions of air molecules against your body. The force of the atmosphere above is weighing down these air molecules.

Air pressure at sea level is measured to be 1 kilogram per square centimeter (14.7 pounds per square inch). This means an air column pressing on 1000 square centimeters (which is a little over one square foot) would weigh one ton. This air pressure at sea level is defined as one atmosphere (1 atm). As you move upwards thorough the atmosphere, the density of air molecules around you decreases. There is also less air above you as you gain altitude. In response, air pressure also decreases with altitude. At an altitude of about 50 kilometers, the atmospheric pressure is just above 0.0009869 atmospheres. At this altitude, you are above 99.9% of the bulk of the atmosphere.

Air Temperature defines the Layers of the Atmosphere

Air temperature is mostly controlled by the absorption of solar energy. This energy is transferred as heat to the atmosphere by the interactions of the greenhouse gases carbon dioxide and water, and at higher altitudes by ozone. The following table lists the various layers of the atmosphere. The boundaries for each layer are defined by the change in atmospheric temperature that happens there.