Environmental Sciences Webex Seminar:
Improving the Representation of Aerosol Emissions and their Radiative Impacts in Climate Models
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Aerosols impact Earth’s climate directly by interacting with radiation and indirectly by affecting cloud microphysics. On top of climate impacts, exposure to air pollution causes more than 8 million premature deaths every year. The radiative and health impacts of aerosols are largely dependent on their source emissions, chemical composition, and microphysics which have yet to be completely characterized. For example, it is largely recognized that sea-spray particles originate from the action of wind stress on the ocean surfaces, however, published parameterizations span nearly one order of magnitude in range and there is no consensus on even the sign of the influence of seawater temperature and biology on sea-spray emissions. My research elucidates some of the key uncertainties regarding sea-spray emissions and shows a positive and significant relationship between sea-spray particle diameter and seawater temperature based on field observations. Additionally, my results suggest that current sea-spray flux parameterizations used in global climate models could underestimate the direct radiative forcing from sea-spray emissions by a factor of 2 to 5 over the North Atlantic.
In this seminar I will also address the poor representation of aerosol emissions from emerging combustion technologies in emission inventories. The newly developed gasoline direct injection engine (GDI) offers significant fuel economy gains compared to other gasoline engines. As a result, the market share of GDI engines in the U.S. has soared in recent years, with GDI engines accounting for more than 50% of newly manufactured engines. However, my research shows that GDI engines emit higher (and more potent light-absorbing) particulate matter emissions, based on a large fleet of vehicle tested in the laboratory. I also show that current emission inventories significantly underestimate tailpipe particulate matter emissions potentially due to the limited testing of these new engines. Such gaps in aerosol emissions and composition have significant air-quality and radiative impacts on a regional scale.