Which factor is most crucial for the creation of tropospheric ozone?

The formation of tropospheric ozone is heavily dependent on the presence of high temperatures and sunlight. These conditions facilitate photochemical reactions, which occur when sunlight interacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx).

During warm, sunny days, the energy from sunlight triggers chemical reactions that convert these precursor pollutants into ozone. Unlike the stratospheric ozone layer, which protects the Earth from harmful UV radiation, tropospheric ozone is an air pollutant that contributes to smog and can have harmful health effects on humans and ecosystems.

In contrast, the other factors listed—moisture and particulates, cold air mass and pressure changes, and low humidity—do not significantly contribute to the photochemical reactions necessary for tropospheric ozone formation. While moisture can influence air quality and particulates may interact with pollutants, it is primarily the combination of high temperatures and abundant sunlight that drives the creation of tropospheric ozone.