The impact of emission and climate change on ozone in the United States under representative concentration pathways (RCPs)

Abstract

Dynamical downscaling was applied in this study to link the global climate-chemistry model Community Atmosphere Model (CAM-Chem) with the regional models Weather Research and Forecasting (WRF) Model and Community Multi-scale Air Quality (CMAQ). Two representative concentration pathway (RCP) scenarios (RCP 4.5 and RCP 8.5) were used to evaluate the climate impact on ozone concentrations in the 2050s. <br><br> From the CAM-Chem global simulation results, ozone concentrations in the lower to mid-troposphere (surface to ~300 hPa), from mid- to high latitudes in the Northern Hemisphere, decreases by the end of the 2050s (2057–2059) in RCP 4.5 compared to present (2001–2004), with the largest decrease of 4–10 ppbv occurring in the summer and the fall; and an increase as high as 10 ppbv in RCP 8.5 resulting from the increased methane emissions. <br><br> From the regional model CMAQ simulation results, under the RCP 4.5 scenario (2057–2059), in the summer when photochemical reactions are the most active, the large ozone precursor emissions reduction leads to the greatest decrease of downscaled surface ozone concentrations compared to present (2001–2004), ranging from 6 to 10 ppbv. However, a few major cities show ozone increases of 3 to 7 ppbv due to weakened NO titration. Under the RCP 8.5 scenario, in winter, downscaled ozone concentrations increase across nearly the entire continental US in winter, ranging from 3 to 10 ppbv due to increased methane emissions. More intense heat waves are projected to occur by the end of the 2050s in RCP 8.5, leading to a 0.3 ppbv to 2.0 ppbv increase (statistically significant except in the Southeast) of the mean maximum daily 8 h daily average (MDA8) ozone in nine climate regions in the US. Moreover, the upper 95% limit of MDA8 increase reaches 0.4 ppbv to 1.5 ppbv in RCP 4.5 and 0.6 ppbv to 3.2 ppbv in RCP 8.5. The magnitude differences of increase between RCP 4.5 and 8.5 also reflect that the increase of methane emissions may favor or strengthen the effect of heat waves

Ozone trends over the United States at different times of day

“…For other seasons, the ozone growth rates decrease drastically from the control to the second case. This reflects "penalty" of reducing NO x (Jhun et al, 2015), which is consistent with previous findings that the 5th percentile of peak ozone (normally occurring in cold seasons) over the eastern US has increased due to weakened NO x titration (Gao et al, 2013;Clifton et al, 2014., Simon et al, 2015Lin et al, 2017).…”

Estimation of future PM2.5- and ozone-related mortality over the continental United States in a changing climate: An application of high-resolution dynamical downscaling technique

“…However, the greenhouse gas emissions of methane show significant increase (about 60%) by the end of the 2050s. More details about emission projections of ozone and PM 2.5 , chemistry downscaling of species mapping, and grid interpolations, together with the evaluation of ozone, have been well documented in Gao et al (2013). Health and environmental assessment modelBenMAP-CE The Environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE 1.0.8; Davidson et al, 2007) was utilized in this study to evaluate the PM 2.5 -and ozone-related mortality for the present and future case. It is a powerful health benefit analysis tool that can estimate the health impacts and economic benefits of human population exposure to air quality (i.e., PM 2.5 and ozone concentration) changes.…”

“…Note that only RCP8.5 scenario is adopted for analysis here, since for the PM precursors, both RCP4.5 and RCP8.5 scenarios project a decrease in the future (Gao et al, 2013). In addition, the greenhouse gas emissions of methane increase more than half in the RCP8.5 scenario, which will lead to enhanced ozone concentration in some seasons and cause more health concerns.…”

Multi-year downscaling application of two-way coupled WRF v3.4 and CMAQ v5.0.2 over east Asia for regional climate and air quality modeling: model evaluation and aerosol direct effects

“…Recently, the online-coupled Weather Research and Forecasting (WRF) model with Chemistry (WRF-Chem) was evaluated for decadal application over the continental US under RCP4.5 and RCP8.5 (Yahya et al, 2016(Yahya et al, , 2017a and applied to decadal projections of future climate and air quality under both scenarios (Yahya et al, 2017b). The Community Multi-scale Air Quality (CMAQ) model has historically been an offline model developed by the US Environmental Protection Agency (EPA) and widely used for air quality simulations over numerous countries and regions (Wang et al, 2009(Wang et al, , 2012Gao et al, 2013;Penrod et al, 2014;Sun et al, 2015;Zheng et al, 2015;Hu et al, 2016); it has recently been further developed to provide an online-coupled version with the Weather Research Forecast (WRF) model to simulate feedbacks between chemistry and meteorology (Wong et al, 2012). Several applications of the two-way coupled WRF-CMAQ model have been conducted to evaluate the performance of the coupled model system and to investigate aerosol direct effects Gan et al, 2015;Hogrefe et al, 2015;Xing et al, 2016) and indirect effects (Yu et al, 2014) on climate and air quality.…”