The Phoenix metropolitan area, like many large cities, has problems with air pollution at certain times of the year. You can do a simple experiment to determine some of the factors that affect air pollution.

Several websites are available that give you access to air quality readings, such as airnow.gov. Most newspapers also publish some air pollution readings on the same page as the weather forecast. However, most of these resources don't store data for you, so you will need to collect your information on several different days, over time. It is best if you record information for days that vary in air quality or weather.

Using information from these sources, try to make a graph of the various items in the weather report and see if you can determine what factors contribute to high pollution days. 

You can usually find information for:

• temperature
• wind speed
• barometric pressure
• carbon monoxide
• particulates

Sometimes ozone is also given.  Ozone, carbon monoxide, and particulates are all considered bad at high levels. 

Try to graph all your different measurements on the same piece of graph paper or the same computer-generated graph. You will see the effect of barometric pressure the best if you will take the reading given in inches and subtract 29 from each reading. That's because there is relatively little variability in barometric pressure when compared to the other readings.

Shanghai image by BriYYZ.