Air Quality & Temperature Correlation?

Question

I notice that whenever the temperature is higher, air quality is stated to be worse when weather forecasts? Is this really the case? And why?

Answer 1

There is a weak correlation between temperature and air quality.  Air quality is worse whenever air is stagnant and not mixing.  An inversion layer can cap the stagnant air mass and further prevent the mixing of the air.  The stronger correlation is between air stagnation and air quality.

Air stagnation often occurs during the summer and early fall months when a large high pressure area develops over large areas of the country.  The presence of a large strong high tends to push low pressure areas around the edges of the high, so the mixing winds caused by a storm circulation are not present to clear out the stagnant air.  Without the low pressure areas and the cleansing rains they bring, the air continues to receive pollutants from the cities, industry, cars, etc, and the air quality continues to deteriorate until air quality alerts are issued.

Hope this helps.

Answer 2

It could be that in some cases the reason it is warmer is due to an inversion above the surface.  This both allows the surface air to warm to a greater amount, as well as serves to trap various particulates and pollutants in the lowest levels of the atmosphere.  In many valley locations, this is actually a problem during the colder times of the year.