Layers of the Air

The atmosphere is not the same at every height. As altitude changes, temperature changes, pressure changes, density changes, and chemical conditions change. The main atmospheric layers are: Troposphere → Stratosphere → Mesosphere → Thermosphere. For environmental chemistry, the two most important layers are: Troposphere → weather and most air pollution; Stratosphere → ozone layer.

Think of the atmosphere as several layers wrapped around Earth. The layer in which we live is called the troposphere. The layer above it, the stratosphere, contains the important ozone layer.

The troposphere is important in environmental chemistry because most human-produced air pollutants are released there. The stratosphere is important because its ozone absorbs harmful ultraviolet radiation. Atmospheric pressure and density decrease as altitude increases.

Atmospheric layers are defined primarily by their thermal structure. The temperature trend changes from one layer to another because different gases absorb different kinds of solar radiation. The stratosphere, for example, shows an unusual temperature increase with altitude partly because ozone absorbs ultraviolet radiation.

No single chemical equation defines atmospheric layers. Increasing altitude: Troposphere < Stratosphere < Mesosphere < Thermosphere.

Troposphere = lowest layer. Most weather occurs in the troposphere. Most ordinary air pollution begins in the troposphere. Stratosphere lies above the troposphere. Ozone layer is mainly in the stratosphere. Pressure and density decrease with altitude.