Urban Ozone Trends in Europe and the USA (2000-2021) 

Speaker:  Beth Nelson and Will Drysdale

Chair(S): Katie Read

wednesday 3rd december, 13:00

ABSTRACT

"Despite global successes in reducing primary pollutant emissions over the past few decades, global exposure to O3 has been increasing throughout the 21st century due to the increasing populations in urban areas. Due to the complexity of O3 production, its trend direction, magnitude, and significance varies by location, but it is important to understand how these trends are behaving to inform future abatement strategies. In this seminar we present a recent study that used surface monitoring site data from the TOAR-II and European Environment Agency databases to conduct trend analysis via piecewise quantile regression at urban ground monitoring stations in Europe (204) the USA (149). We found that there were many sites across Europe with high certainty increasing trends in the 5th and 50th quantiles, whereas the majority of high certainty trends in the 95th quantile were found to be decreasing. A similar pattern was observed across the USA, with 5th quantile trends increasing and 95th quantile trends decreasing, though a small but increasing number of sites showed a return to increasing trend at τ = 95.  Trends were grouped via dynamic time warping and hierarchical clustering, helping to isolate geographic groups. Increasing trends were identified across southern and the central alpine regions of Europe, and in California and the Intermountain West of the USA. "

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