AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Enhanced Characterization of Particle Size Distribution in the Community Multiscale Air Quality Model (CMAQ): A Case Study of Commercial Aircraft Emissions
HUANG JIAOYAN, Lakshmi Pradeepa Vennam, Benjamin Murphy, Francis Binkowski, Saravanan Arunachalam, University of North Carolina, Chapel Hill
Abstract Number: 73 Working Group: Regional and Global Air Quality and Climate Modeling
Abstract Currently, the Community Multiscale Air Quality Model (CMAQ) treats particles size distribution without considering variations in particle size distribution (PSD) from individual emission sectors. Individual source sectors have varying PSD, and having a constant PSD for all source sectors might lead to uncertainties in predicted aerosol characteristics – number and mass concentrations. Prior work has shown that ultrafine particles (UFP) mass concentrations are underestimated from emissions in current CMAQ configuration. In this study, a new CMAQ module was developed to read particle emissions from a specific sector, and treat its PSD separately. Impacts on ambient particulate matter due to commercial aircraft emissions in North America were investigated using this new module, and based upon information on aircraft emissions characteristics from engine measurement campaigns. Three scenarios were simulated: nonaircraft (all anthropogenic and biogenic emissions except aircraft emissions), base (nonaircraft and aircraft emissions with uniform particle size distribution called the default configuration), and sensitivity (nonaircarft and aircraft emissions with two different PSDs) scenarios. Total and aircraft attributed number concentrations of UFP are improved using this new CMAQ module. Number concentrations of UFP dramatically increase in the immediate vicinity of the airport locations due to changes in aircraft emitted PSD. Number concentrations of UFP in LAX from sensitivity scenario are 5.2 times higher than from nonaircraft scenarios. This finding matches the observation in recent field measurements of UFP due to aircraft emissions. Although mass concentrations in accumulation modes in airports were marginally lower, values in UFP were higher in sensitivity than in base scenarios. This study is the first CMAQ-based study to look into ambient particle matter impacted by PSD changes in emissions from an individual source sector. Shifting particles to small size increases available surface areas which can impact deposition, aerosol chemistry and gas-particle partitioning processes. We will present results from this study focusing on UFP impacts both from US-wide aircraft activity as well as at individual large airports.