“…Satellite-and ground-based observations imply significant declines in US NO x emissions, with a decreasing rate of roughly −4 % yr −1 after 2005 (Krotkov et al, 2016;Russell et al, 2012;Tong et al, 2015;Miyazaki et al, 2017;Lu et al, 2015;Lamsal et al, 2015). This has proven effective at lowering near-surface ozone (O 3 ) in the past few decades (Cooper et al, 2012;Simon et al, 2015;Hidy and Blanchard, 2015;Stoeckenius et al, 2015;Xing et al, 2015;Yahya et al, 2016;Astitha et al, 2017). The average of the annual fourth highest daily maximum 8 h average (MDA8) ozone over 206 sites has decreased by 31 % from 101 ppb in 1980 to 70 ppb in 2016 across the continental US, with more significant reductions in rural areas of the eastern US in summer (Simon et al, 2015;Cooper et al, 2012).…”