What is Smog and Temperature Inversion

When a layer of air may lies over a city like Los Angeles, it can trap thick, pollutant-rich air near the ground, a form of pollution we call smog.
In the usual course of things, the sun warms Earth, and that warm air expands and rises.
It cools as it rises, losing about 3.5 degrees Fahrenheit with every thousand feet of elevation.
But certain condition can disrupt this order. Land warms up in the sun much faster than water and becomes less dense.
So in the Los Angeles Basin, for example, cool sea breezes sweeping inland easily wedge themselves beneath this warmer air.
At the same time, air warmed on the high deserts around the city is lifted up against mountains ringing from city and slides in on top of the cooler air over Los Angeles.
This warm inversion layer, ad it's called, acts like a lead, blocking the vertical circulation of air—and trapping pollutants from the welter of fossil fuel-burning vehicles.