Source attribution of European surface O<sub>3</sub> using a tagged O<sub>3</sub> mechanism

Abstract

Tropospheric ozone (O 3 ) is an important air pollutant that affects human health, ecosystems, and climate. The contributions of O 3 precursor emissions from different geographical source regions to the O 3 concentration can help to quantify the effects of local versus remotely transported precursors on the O 3 concentration in a certain area. This study presents a "tagging" approach within the WRF-Chem model that attributes O 3 concentration in several European receptor regions to nitrogen oxide (NO x ) emissions from within and outside of Europe during April-September 2010. We also examine the contribution of these different precursor sources to various O 3 metrics and their exceedance events. Firstly, we show that the spatial distributions of simulated monthly mean MDA8 from tagged O 3 source regions and types for late spring, summer, and early autumn 2010 varies with season. For summer conditions, O 3 production is dominated by national and intra-European sources, while in the late spring and early autumn intercontinental transported O 3 is an important contributor to the total O 3 concentration. We have also identified shipping activities in the Mediterranean Sea as an important source of O 3 for the Mediterranean countries, as well as the main contributor to high modelled MDA8 O 3 concentration in the Mediterranean Basin itself. Secondly, to have a better understanding of the origin of MDA8 O 3 exceedances, we compare modelled and observed values of MDA8 O 3 concentration in the Po Valley and Germany-Benelux receptor regions, revealing that the contribution from local sources is about 41 % and 38 % of modelled MDA8 O 3 during the exceedance days, respectively. By examining the relative contributions of remote NO x sources to modelled and observed O 3 exceedance events, we determine that model underrepresentation of long-range O 3 trans-port could be contributing to a general underestimation of modelled O 3 exceedance events in the Germany-Benelux receptor region. Thirdly, we quantify the impact of local vs. non-local NO x precursors on O 3 production for each European receptor region using different O 3 metrics. The comparison between mean, MDA8 and 95th percentile O 3 metrics accentuates the importance of large contributions from locally emitted NO x precursors to the high end of the O 3 distribution. When we compare the vegetation and health metrics, we notice that the SOMO35 and AOT40 indexes exhibit rather similar behaviour, while the W126 index accentuates the importance of local emissions. Overall, this study highlights the importance of a tagging approach to quantify the contribution of local and remote sources to the MDA8 O 3 concentration during several periods as well to different O 3 metrics. Moreover, this method could be applied to assess different mitigation options.Published by Copernicus Publications on behalf of the European Geosciences Union.

Attribution of ground-level ozone to anthropogenic and natural sources of NO<sub>x</sub> and reactive carbon in a global chemical transport model

“…shows a similar magnitude for the influence of ship NO x on summertime ozone in Europe as for springtime ozone. Lupaşcu and Butler (2019), using a regional model at 50×50 km resolution and a similar ozone tagging system as used in the present study, showed that the contribution of ship NO x to ozone in coastal regions of Europe reaches a maximum level in summer. Jonson et al (2020), using a global model with a resolution of 0.5 × 0.5 degrees showed that shipping near coastal regions contributes significantly to ozone over North West Europe in both spring and summer, while NO x emissions from shipping on the high seas makes a stronger contribution to European ozone in spring than in summer.…”

Review

“…The ap-C2 proaches shared by Dunker et al (2002) and Kwok et al (2015), which tag ozone based on the chemical regime are both well-established and should be referenced in any discussion of modelled source attribution. Yet another approach was described recently by Butler et al (2018) and has been applied by Lupascu et al (2019).…”

“…The authors are right that large number of tracers can rapidly make tagging computationally expensive, but they should also point out that techniques exist to keep these problems in check. For example Butler et al (2018) Restrict the number of tracers to a carefully chosen set of representative source sectors; Grewe et al (2017) make use of the concept of "chemical families" to keep the number of tagged species within reasonable limits; and Lupascu et al (2019) restrict the length of their simulation period to focus on a pollution episode of interest. Each of these approaches brings different trade-offs, but in each case also significant advantages: the ability to perform source attribution for secondary pollutants; and the ability to perform source attribution for long-range transport.…”

The impact of atmospheric blocking on the compounding effect of ozone pollution and temperature: a copula-based approach

“…Copula-based methods have been extensively applied in hydrological extremes (Salvadori and Michelle, 2010;Hao et al, 2018) and provide a flexible method of construction for a joint distribution with arbitrary marginal distributions (AghaKouchak et al, 2014). Copulas describe the dependence between random variables (Nelsen, 2006) and, besides characterising the overall dependence structure, certain copula families allow the upper tail dependence to be measured, which is particularly important for assessing extreme events (Zscheischler and Seneviratne, 2017;Serinaldi, 2016). Therefore, with the main goal of estimating the effects of atmospheric blocking on the relationship between ozone and temperature, we apply a copula-based approach that allows us to quantify the influence of atmospheric blocking on the upper tail of the joint distribution of ozone and temperature.…”