How to Locate a Capping Inversion

Look for smog. Smog is visible air pollution -- smoke and other particles and gases -- that becomes trapped under a capping inversion. This weather condition occurs readily in cities such as Los Angeles and Mexico City that are surrounded by mountains or even low hills that obstruct air circulation.

Look for fog. Fog is cool air supersaturated with moisture and held in place by a capping inversion. In coastal cities such as San Francisco, the water-cooled marine layer supplies moisture from the ocean, while the inland hills not only radiate solar heat that warms air to override the cool layer but also shield the city from air currents that would break up the capping inversion.

Look for clouds. Clouds are a negative indicator for a capping inversion, as they form only in rising air currents and where there are air currents, there is no "lid."