What is the primary function of polar stratospheric clouds (PSCs) in relation to ozone depletion?

The primary function of polar stratospheric clouds (PSCs) in relation to ozone depletion is to facilitate the breakdown of ozone molecules. These clouds form in the extremely cold conditions of the polar stratosphere and are composed of ice crystals and other chemical components. Their presence is critical in the process of ozone depletion because they provide a surface for chemical reactions to occur.

In the presence of PSCs, chlorine compounds, which are often derived from human-made substances like chlorofluorocarbons (CFCs), can become activated. When sunlight returns to the poles in the spring, it initiates the breakdown of these compounds, releasing active chlorine. This active chlorine is highly effective at catalyzing the destruction of ozone (O3) in the stratosphere. One chlorine atom can destroy thousands of ozone molecules before it is deactivated.

Thus, the role of PSCs is pivotal in the photochemical reactions that lead to the depletion of the ozone layer. This is a significant environmental concern, as the ozone layer protects the Earth from harmful ultraviolet (UV) radiation.