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- Title
Disentangling the Drivers of the Summertime Ozone‐Temperature Relationship Over the United States.
- Authors
Kerr, Gaige Hunter; Waugh, Darryn W.; Strode, Sarah A.; Steenrod, Stephen D.; Oman, Luke D.; Strahan, Susan E.
- Abstract
Summertime surface‐level ozone (O3) is known to vary with temperature, but the relative roles of different processes responsible for causing the O3‐temperature relationship are not well quantified. In this study we use simulations of NASA's Global Modeling Initiative chemical transport model to isolate and assess the relative impact of atmospheric transport, chemistry, and emissions on large‐scale O3 variability, events, and and the covariance of O3 with temperature. Using observations from the Clean Air Status and Trends Network in the contiguous United States, we show that the Global Modeling Initiative chemical transport model reproduces the spatiotemporal variability of O3 and its relationship with temperature during the summer. We use the change in O3 given a change in temperature (dO3/dT) along with other metrics to understand differences between our simulations. In regions with moderate to strong positive correlations between temperature and O3 such as the northeast, Great Lakes, and Great Plains, temperature's association with transport yields a majority of the total O3‐temperature relationship (∼60%), while temperature‐dependent chemistry and anthropogenic NO emissions play smaller roles (∼30% and ∼10%, respectively). There are regions, however, with insignificant correlations between temperature and O3, and our findings suggest that transport is still an important driver of O3 variability in these regions, albeit not correlated with temperature. Transport is not directly dependent on temperature but rather is linked through an indirect association, and it is therefore important to understand the exact mechanisms that link transport to O3 and how these mechanisms will change in a warming world. Plain Language Summary: Ozone near the Earth's surface is a harmful air pollutant as well as a greenhouse gas. Ozone generally increases on hot days as the result of certain meteorological conditions, chemistry, and emissions; thus, researchers have speculated that global warming will guarantee increases of ozone. This assumption hinges on the relationship of temperature with meteorology, chemistry, and emissions and its effect on ozone, and these relationships might change in the future. In our research, we use observations and detailed computer model simulations to understand the roles that meteorology, chemistry, and emissions contribute to the ozone‐temperature relationship. We find that atmospheric transport—that is, how horizontal and vertical motions transport and disperse ozone in the atmosphere—is the key player in explaining the ozone‐temperature relationship throughout much of the United States. However, transport does not directly lead to increased ozone; rather, certain types of transport are associated with high or low ozone, and, because of this indirect association, our results illustrate the need to better understand how transport affects ozone and how this will change in the future. Key Points: Model simulations reproduce the large‐scale distribution of O3 and its covariance with temperatureIn regions where the O3‐temperature correlation is strongly positive, transport drives the O3‐temperature relationshipFuture changes of dO3/dT are uncertain due to the indirect association of O3 and transport
- Subjects
OZONE; UNITED States. National Aeronautics &; Space Administration; GLOBAL modeling systems; CHEMICAL transportation; SPATIOTEMPORAL processes
- Publication
Journal of Geophysical Research. Atmospheres, 2019, Vol 124, Issue 19, p10503
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2019JD030572