10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Regional Climate and Air Quality Impacts of Particulate Emissions from Gasoline Direct-Injection (GDI) Vehicles
SOROUSH ESMAEILI NEYESTANI, Rawad Saleh, University of Georgia
Abstract Number: 458 Working Group: Aerosol Modeling
Abstract Due to their enhanced fuel economy, the market share of Gasoline Direct-Injection (GDI) engines light-duty vehicles has increased noticeably over the past decade. However, compared to the traditional port-fuel injection (PFI) engines, GDI engines have been shown to emit higher levels of particulate matter, especially black carbon (BC). BC is an efficient absorber of solar radiation, and is a prominent global-warming agent second only to carbon dioxide. This competing effect of reducing carbon dioxide emissions but increasing BC emissions raises a question regarding the net climate impacts of GDI vehicles. Back-of-envelope calculations based on the global-warming potential (GWP) of BC have shown that, on a global scale, switching to GDI vehicles has a net climate benefit of 0.5% – 2.4%1,2. However, due to their short lifetime, aerosol climate impacts are more important on the regional scale; therefore, the regional climate impacts of GDI vehicles might diverge from the global impacts in areas where traffic emissions are prominent. Here, we estimate the regional (over the United States) air quality and climate impacts of switching the U.S. fleet from PFI to GDI vehicles. We use the Weather Research and Forecasting model coupled with chemistry (WRF-Chem), which simulates both chemical transport and radiative transfer. The simulations are performed at a 12 km resolution and for a period of four months (February, May, August, and November) in each season of 2011 to take into account the seasonal variability. Rapid Radiation Transfer Model for GCM (RRTMG) and Modal Aerosol Dynamic for Europe coupled with Secondary Organic Model (MADE-SORGAM) schemes are used in the model for SW/LW atmospheric radiation and aerosol mechanism, respectively. Aerosol Optical Depth (AOD) retrieved from NASA’s Aerosol Robotic Network (AERONET) and Moderate Resolution Imaging Spectroradiometer (MODIS) are used to validate model calculations. Using the EPA’s National Emission Inventory for 2011 (NEI-2011) as a base case, we modify the vehicle emission profiles using GDI emission data from measurements1. By comparing the base case with the modified one, we obtain spatially and seasonally resolved changes in carbonaceous aerosol concentrations and the consequent radiative effect.
References: 1. Saliba, G. et al. Comparison of Gasoline Direct-Injection (GDI) and Port Fuel Injection (PFI) Vehicle Emissions: Emission Certification Standards, Cold-Start, Secondary Organic Aerosol Formation Potential, and Potential Climate Impacts. Environ. Sci. Technol. 51, 6542–6552 (2017). 2. Zimmerman, N., Wang, J. M., Jeong, C. H., Wallace, J. S. & Evans, G. J. Assessing the Climate Trade-Offs of Gasoline Direct Injection Engines. Environ. Sci. Technol. 50, 8385–8392 (2016).