Abstract
Surface ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity. The Tropospheric Ozone Assessment Report (TOAR) is designed to provide the research community with an up-to-date observation-based overview of tropospheric ozone’s global distribution and trends. The TOAR Surface Ozone Database contains ozone metrics at thousands of monitoring sites around the world, densely clustered across mid-latitude North America, western Europe and East Asia. Calculating regional ozone trends across these locations is challenging due to the uneven spacing of the monitoring sites across urban and rural areas. To meet this challenge we conducted a spatial and temporal trend analysis of several TOAR ozone metrics across these three regions for summertime (April–September) 2000–2014, using the generalized additive mixed model (GAMM). Our analysis indicates that East Asia has the greatest human and plant exposure to ozone pollution among investigating regions, with increasing ozone levels through 2014. The results also show that ozone mixing ratios continue to decline significantly over eastern North America and Europe, however, there is less evidence for decreases of daytime average ozone at urban sites. The present-day spatial coverage of ozone monitors in East Asia (South Korea and Japan) and eastern North America is adequate for estimating regional trends by simply taking the average of the individual trends at each site. However the European network is more sparsely populated across its northern and eastern regions and therefore a simple average of the individual trends at each site does not yield an accurate regional trend. This analysis demonstrates that the GAMM technique can be used to assess the regional representativeness of existing monitoring networks, indicating those networks for which a regional trend can be obtained by simply averaging the trends of all individual sites and those networks that require a more sophisticated statistical approach.
Highlights
Tropospheric ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity (REVIHAAP, 2013; U.S Environmental Protection Agency, 2013; LRTAP Convention, 2015; Monks et al, 2015)
This paper aims to answer these questions by applying a generalized additive mixed model (GAMM) to determine the systematic regional variations of several ozone metrics across eastern North America, Europe and East Asia
In order to alleviate the linear constraints in the generalized linear model (GLM), the generalized additive model (GAM) allows that one or more covariates depend on nonparametric smooth functions
Summary
Tropospheric ozone is a greenhouse gas and pollutant detrimental to human health and crop and ecosystem productivity (REVIHAAP, 2013; U.S Environmental Protection Agency, 2013; LRTAP Convention, 2015; Monks et al, 2015). Since 1990 a large portion of the anthropogenic reactive gas emissions that produce ozone have shifted from North America and Europe to Asia (Granier et al, 2011; Cooper et al, 2014; Zhang et al, 2016) This rapid shift, coupled with limited ozone monitoring in University of Colorado, Boulder, US ‡ Institute for Energy and Climate Research (IEK-8), Forschungszentrum Jülich, Jülich, DE § Department of Civil and Environmental Engineering, The Hong developing nations, presents a challenge to the scientists trying to summarize and understand recent changes in ozone at the global scale. These ozone metrics are freely accessible for research on the global-scale impact of ozone on climate, human health and crop/ecosystem productivity (Schultz et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
