Episodic Ozone Pollution in the Lower Fraser Valley, BC: A Tale of Three Episodes Moisseeva, Nadya
The spatiotemporal characteristics of episodic ozone pollution in the Lower Fraser Valley of British Columbia have changed markedly over the past two decades. These changes are documented by Ainslie and Steyn (2007), who hypothesize that they have come about because of reductions in ozone precursor emissions strength, driven by aggressive air quality management plans. This study sheds further light on this phenomenon by a parallel spatiotemporal analysis of three notable episodes, one in 1988, one in 1998 and one in 2009. These three episodes span the emissions reductions initiatives, and the analysis is designed to cast light on potential for future air quality management strategies. The analysis is based on a combined air quality and meteorological definition of an ozone episode. This paper investigates the particular meteorological conditions during each of these episodes, and shows that the most recent episode is characterized by record high temperatures, and suppression of the mixed layer, distinct from other episodes. In spite of reduced total emissions, the unusual meteorological conditions provide a context in which ozone pollution can still exceed applicable standards. The paper speculates on the implications for ozone pollution episodes in changed climates.
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