Publication Date:
2014-03-28
Description:
This study uses a regional fully coupled chemistry-transport model to assess changes in surface ozone over the summertime U.S. between present and a 2050 future time period at high spatial resolution (12 km grid spacing) under the SRES A2 climate and RCP8.5 anthropogenic precursor emission scenario. The impact of predicted changes in regional climate and globally enhanced ozone is estimated to increase surface ozone over most of the U.S; the 5 th - 95 th percentile range for daily 8-hour maximum surface ozone increases from 31-79 ppb to 30-87 ppb between the present and future time periods. The analysis of a set of meteorological drivers suggests that these mostly will add to increasing ozone, but the set of simulations conducted is targeted on understanding the competing effect of global versus local emission changes and does not allow separating the meteorological feedbacks from that due to enhanced global ozone. Statistically significant increases were found for future temperature, biogenic emissions and solar radiation. Stringent emission controls can counteract these likely positive feedbacks and if implemented as in RCP8.5, we estimate large reductions in surface ozone with the 5 th -95 th percentile reduced to 27-55 ppb. A comparison of the high-resolution projections to global model projections shows that the global model has a high positive bias in surface ozone compared to the regional model and compared to observations. On average, both the global and the regional model predict similar changes in ozone between the present and future time periods. However, on small spatial scales, the regional model shows pronounced differences between projections in urban and rural regimes that cannot be resolved at the coarse (2°x2°) resolution of the considered global model. This study confirms the key role of emission control strategies in future air quality projections and demonstrates the need for considering degradation of air quality with future climate change in emission policy making. It also illustrates the need for high resolution modeling when the objective is to address regional and local air quality or establish links to human health and society.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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