Atmospheric Inversion
If you can smell smoke in the air on a cool morning, it is likely that there is a temperature inversion , which can occur when a layer of warmer air traps a cooler layer near the surface. During an inversion, there is a high probability of fog. Also sound travels farther and can be heard more loudly.
The above is from the lesson I taught on reading weather, below is a deeper explanation of what a Atmospheric Inversion is and how they occur.
Atmospheric inversions are horizontal layers of air that increase in temperature with height. Such warm, light air often lies over air that is cooler and heavier. As a result the air has a strong vertical stability, especially in the absence of strong winds.
Atmospheric inversions play an important role in air quality . They can trap air pollutants below or within them, causing high concentrations in a volume of air that would otherwise be able to dilute air pollutants throughout a large portion of the troposphere.
Alternatively, relatively warm air may flow over a cold surface with the same results. Elevated atmospheric inversions can occur when vertical differences in wind direction allow warm air to set up over cold air. However, it is more common in near-subtropical latitudes, especially on the western sides of continents, to get subtropical subsidence inversions. Subtropical subsidence inversions often team with mountainous topography to trap air both horizontally and vertically.
