A Statistical Framework to Identify the Influence of Large-Scale Weather Events on Regional Air Pollution

Abstract

Regional air pollution episodes occur as a result of increased emissions and prevalence of conducive meteorological conditions. The frequency of occurrence of such favorable conditions on a regional scale may be influenced by large-scale climatic events like ENSO and the Pacific decadal oscillation(PDO).The scarcity of measurements of criteria pollutants, especially ozone and particulate matter (PM), prior to the last 10–15-yr period, limits the scope of observing the influence of climate variability during recent decades on regional pollution levels. The authors propose a novel statistical framework to utilize available measurements and characterize synoptic influences on regional PM pollution in California’s Central Valley during 1998–2008. The identified target conditions are used to develop a classification scheme to scan historical climate datasets dating back to 1948. The procedure identifies exceedance-conducive days during 1950–98, when no PM2.5 measurements were available. Temporal patterns in seasonal frequency of these identified exceedance conducive days are investigated for temporal patterns driven by ENSO and PDO.