Climatic variability and its influence on ozone and PM pollution in 6 non-attainment regions in the United States

Regional ozone and particulate matter (PM) pollution have a strong dependence on prevailing meteorological conditions. The occurrence of favorable conditions on a regional scale may be influenced by concurrent large scale climatic events like El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). These events evolve over inter-annual and decadal timescales and may result in variability of seasonal/annual frequency of air pollution episodes. The scarcity of measurements of criteria pollutants, especially ozone and PM, limits the scope of observing the influence of climate variability in the past few decades on regional pollution levels. To identify these trends, the frequency of occurrence of conducive conditions during the summer (ozone) and winter (PM2.5) seasons are first obtained for the period 1950–2008. The identified days are subsequently utilized in a generalized linear modeling (GLM) framework to identify the effects of ENSO and PDO on the occurrence of exceedence conducive days. To demonstrate the applicability of the developed methodology, we study the influence of ENSO and PDO on summer ozone and winter PM2.5 pollution at 6 non-attainment regions in the United States.