The stratosphere exhibits a positive lapse rate of temperature, meaning temperature increases with altitude, contrary to the troposphere where temperature decreases with altitude. This unique characteristic is due to the presence of the ozone layer.

Here's why:

1. Ozone Layer: The stratosphere contains a high concentration of ozone (O3) gas. This ozone layer absorbs ultraviolet (UV) radiation from the sun.

2. UV Absorption: When UV radiation strikes ozone molecules, it causes them to split and recombine, releasing heat energy in the process. This energy warms the surrounding air, leading to a temperature increase.

3. Temperature Profile: This heating effect of the ozone layer creates a temperature inversion, where temperatures rise with altitude. The upper stratosphere can reach temperatures as high as 0°C (32°F) or even higher.

4. Stable Atmosphere: This positive lapse rate contributes to a very stable atmosphere in the stratosphere. Since warm air is less dense than cold air, the air in the stratosphere is less likely to mix vertically, resulting in a relatively calm and stable layer.

In summary, the positive lapse rate in the stratosphere is primarily caused by the absorption of UV radiation by the ozone layer, which heats the surrounding air and creates a temperature inversion.