Understanding New Particle Formation and Growth during the HI-SCALE 2016 Field Campaign over the Southern Great Plains (SGP) Region

MANISHKUMAR SHRIVASTAVA, Jie Zhang, Rahul Zaveri, Bin Zhao, Alla Zelenyuk, John Shilling, Jerome Fast, Brian Gaudet, Jeffrey R. Pierce, Havala Pye, Benjamin Murphy, Pacific Northwest National Laboratory

     Abstract Number: 117
     Working Group: Aerosols Spanning Spatial Scales: Measurement Networks to Models and Satellites

Abstract
New particle formation (NPF) and growth govern cloud condensation nuclei (CCN) in many regions. The mechanisms governing the nucleation of molecular clusters vary substantially in different regions of the atmosphere. Additionally, the growth of these clusters to CCN sizes is often governed by the availability of extremely low volatility organic vapors (ELVOCs) formed by oxidation of volatile organic gases (VOCs) emitted from natural biogenic and anthropogenic sources. While the pathways to ELVOC formation from the oxidation of biogenic monoterpenes with ozone is better understood, the chemical and mechanistic pathways for ELVOC formation from oxidation of anthropogenic organics are not well understood. We integrate measurements and three-dimensional regional model simulations with the Weather Research and Forecasting Model coupled to chemistry (WRF-Chem) to understand the processes governing new particle formation and growth and SOA formation during the HI-SCALE field campaign at the Southern Great Plains observatory in Oklahoma, USA. Among our 8 different nucleation mechanisms that include organic- and inorganic- neutral and ion induced processes, we find that the amine+H2SO4 is the major nucleation mechanism near the surface. Through various WRF-Chem sensitivity simulations, we find that anthropogenic ELVOCs are critical for explaining the observed number size distribution of particles near the surface at the SGP site during the daytime. Our simulations show that volatile chemical products (VCPs) and mobile sources substantially contribute to anthropogenic secondary organic aerosols (SOA) over the SGP region, and their aging to ELVOCs is critical for explaining particle size distributions. On different days variations in the contributions of anthropogenic, biogenic, biomass burning SOA to particle growth is manifested in the particle size distributions and chemical composition observed by ground-based and aircraft measurements with the DOE G-1 aircraft during HI-SCALE.