A volatility basis set model for summertime secondary organic aerosols over the eastern United States in 2006

Abstract

[1] A new secondary organic aerosol (SOA) parameterization based on the volatility basis set is implemented in a regional air quality model WRF-CHEM. Full meteorological and chemistry simulations are carried out for the United States for August-September 2006. Predicted organic aerosol (OA) concentrations are compared against surface measurements made by several networks and aircraft data from the TexAQS-2006 field campaign. Elemental carbon simulations are also evaluated in order to evaluate the model's ability to capture their emissions, transport, and removal. Certain measurement limitations, such as daily averaged OA concentrations, impose some difficulties on the model evaluation, and hourly averaged OA measurements provide more informative constraints compared to daily concentrations. The updated model demonstrates a significant improvement in simulating the OA concentrations compared to the standard WRF-CHEM, which predicts very little SOA. The improvement in organic carbon (OC) predictions is noticeable in correlations and model bias. The correlations of OC exceed that of the persistence forecasts for hourly concentrations in the southeast United States during daytime. The updated traditional SOA yields still lead to an underestimation of observed OA, while addition of the multigenerational volatile organic compound (VOC) oxidation drastically improves model performance. However, several key uncertainties remain in SOA formation and loss mechanisms, which are characterized through several perturbation simulations. Dry deposition of VOC oxidation products is an important factor in the atmospheric SOA budget. The combination of the biogenic VOC emissions, updated SOA yields, and aging mechanism result in biogenic SOA being the dominant OA component for much of the nonurban United States.

Sources and Characteristics of Summertime Organic Aerosol in the Colorado Front Range: Perspective from Measurements and WRF-Chem Modeling

“…The model also contains the state of the art SOA schemes based on a volatility basis set approach. In this study, we used an SOA scheme mostly based on the RACM_SOA_VBS mechanism described in Ahmadov (2012). In the model, five volatility bins (10 -1 , 10 0 , 10 1 , 10 2 ,…”

“…Similar to other aerosol particles, SOA particles deteriorate air quality and visibility and impact the climate directly through absorption and scattering of radiation and indirectly through interactions with clouds (Monks et al, 2009). Despite recent advances in the measurement and modeling aspects of SOA and their precursors (e.g., Donahue et al, 2006;Ervens and Volkamer 15 2010;Hodzic et al, 2010a;de Gouw et al, 2011;Hodzic and Jimenez 2011;Shrivastava et al, 2011;Ahmadov et al, 2012;Isaacman et al, 2012;Yatavelli et al, 2012;Ehn et al, 2014;Ensberg et al, 2014;Fast et al, 2014;Lopez-Hilfiker et al, 2014;Williams et al, 2014), the full extent of SOA sources, formation processes, and therefore their impact on air quality, human health, and climate are not fully understood.…”

ORACLE 2-D (v2.0): an efficient module to compute the volatility and oxygen content of organic aerosol with a global chemistry–climate model

“…3370 A. P. : an efficient module to compute volatility and oxygen content approach, semi-volatile primary emissions, chemical aging, and SOA formation were unified within a common framework that is ideally suited for regional and global chemical modeling. Since 2006, many regional (Lane et al, 2008;Murphy and Pandis, 2009;Tsimpidi et al, , 2011Ahmadov et al, 2012;Athanasopoulou et al, 2013;Koo et al, 2014;Fountoukis et al, 2014;Ciarelli et al, 2017;Gao et al, 2017) and global (Pye and Seinfeld, 2010;Jathar et al, 2011;Jo et al, 2013;Tsimpidi et al, 2014;Hodzic et al, 2016) modeling studies have used the VBS to account for the semi-volatile nature and chemical aging of organic compounds, demonstrating improvements in reproducing the OA budget and its chemical resolution.…”

Rapid deposition of oxidized biogenic compounds to a temperate forest

“…It has been postulated that dry deposition may be a significant sink for many key OVOCs within the boundary layer and thus may be a controlling factor for their atmospheric lifetimes and mixing ratios at Earth's surface. Furthermore, atmospheric model evaluations suggest that disregarding dry deposition of OVOCs may lead to a large overestimate in the formation rate of secondary organic aerosol (up to 50%) (11,12), a larger error than that due to ignoring wet deposition (13).…”