Quantify the Relationship between Extreme Air Pollution Events and Extreme Weather Events

Meteorological processes on various scales strongly affect air quality, in particular surface ozone and Particular Matter (PM) concentrations. To understand their relationship and provide insight for future climate projection, we conducted a quantitative study of the severe air pollution events and extreme weather events based on historical observations. The 8-hr average ozone maximum concentration and 24-hr geometric mean concentration of PM2.5 from the EPA Air Quality System (AQS) were selected as the major air quality indices. The maximum temperature and precipitation rate from the high resolution Climate Forecast System Reanalysis (CFSR) were used to represent local meteorological condition. An extreme event was defined using the threshold of 95% percentile for a particular index within the entire data period, which was 30 years (1980-2009) for ozone concentrations and 10 years (2000-2009) for PM2.5 concentrations. Occurrences of extreme weather events and extreme ozone/PM2.5 events were compared. The duration, frequency, magnitude, and spatial-temporal scales of extreme events were examined.