The mechanisms and meteorological drivers of the summertime ozone–temperature relationship
<p>Surface ozone (<span class="inline-formula">O<sub>3</sub></span>) pollution levels are strongly correlated with daytime surface temperatures, especially in highly polluted regions. This correlation is nonlinear and occurs through a variety of temperature-de...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/13367/2019/acp-19-13367-2019.pdf |
| Summary: | <p>Surface ozone (<span class="inline-formula">O<sub>3</sub></span>) pollution levels are strongly
correlated with daytime surface temperatures, especially in highly polluted
regions. This correlation is nonlinear and occurs through a variety of
temperature-dependent mechanisms related to <span class="inline-formula">O<sub>3</sub></span> precursor emissions,
lifetimes, and reaction rates, making the reproduction of temperature
sensitivities – and the projection of associated human health risks – a
complex problem. Here we explore the summertime <span class="inline-formula">O<sub>3</sub></span>–temperature
relationship in the United States and Europe using the chemical transport
model GEOS-Chem. We remove the temperature dependence of several mechanisms
most frequently cited as causes of the <span class="inline-formula">O<sub>3</sub></span>–temperature “climate
penalty”, including PAN decomposition, soil <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions, biogenic volatile organic compound (VOC)
emissions, and dry deposition. We quantify the contribution of each
mechanism to the overall correlation between <span class="inline-formula">O<sub>3</sub></span> and temperature both
individually and collectively. Through this analysis we find that the
thermal decomposition of PAN can explain, on average, 20 % of the overall
<span class="inline-formula">O<sub>3</sub></span>–temperature correlation in the United States. The effect is weaker
in Europe, explaining 9 % of the overall <span class="inline-formula">O<sub>3</sub></span>–temperature relationship.
The temperature dependence of biogenic emissions contributes 3 % and 9 %
of the total <span class="inline-formula">O<sub>3</sub></span>–temperature correlation in the United States and Europe
on average, while temperature-dependent deposition (6 % and 1 %) and
soil <span class="inline-formula">NO<sub><i>x</i></sub></span> emissions (10 % and 7 %) also contribute. Even considered
collectively these mechanisms explain less than 46 % of the modeled
<span class="inline-formula">O<sub>3</sub></span>–temperature correlation in the United States and 36 % in Europe.
We use commonality analysis to demonstrate that covariance with other
meteorological phenomena such as stagnancy and humidity can explain the bulk
of the remainder of the <span class="inline-formula">O<sub>3</sub></span>–temperature correlation. Thus, we
demonstrate that the statistical correlation between <span class="inline-formula">O<sub>3</sub></span> and temperature
alone may greatly overestimate the direct impacts of temperature on <span class="inline-formula">O<sub>3</sub></span>,
with implications for the interpretation of policy-relevant metrics such as
climate penalty.</p> |
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| ISSN: | 1680-7316 1680-7324 |