Abstract
Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are 10s of kilometers and larger. The predictive power of these models is thus limited by the resultant uncertainties in aerosol size distributions. In this paper, we focus on sub-grid sulfate aerosol processes within coal-fired power plant plumes: the sub-grid oxidation of SO2 with condensation of H2SO4 onto newly-formed and pre-existing particles. We have developed a modeling framework with aerosol microphysics in the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM). The model is evaluated against aircraft observations of new-particle formation in two different power-plant plumes and reproduces the major features of the observations. We show how the downwind plume aerosols can be greatly modified by both meteorological and background aerosol conditions. In general, new-particle formation and growth is greatly reduced during polluted conditions due to the large pre-existing aerosol surface area for H2SO4 condensation and particle coagulation. The new-particle formation and growth rates are also a strong function of the amount of sunlight and NOx since both control OH concentrations. The results of this study highlight the importance for improved sub-grid particle formation schemes in regional and global aerosol models.
Highlights
It has been established that aerosols have a cooling effect on climate through the direct and indirect aerosol effects, but the magnitude of these effects is still very uncertain (Solomon et al, 2007)
To better understand the number and size of particles that should be effectively emitted from anthropogenic sources in regional and global models, we explore the evolution of the number and size of sulfate aerosol particles inside coal-fired power-plant plumes using a 3-D fluid-dynamics model of plume chemistry and physics: the System for Atmospheric Modelling (Kairoutdinov and Randall, 2003) with TwO Moment Aerosol Sectional (Adams and Seinfeld, 2002) microphysics (SAM-TOMAS)
In order to study nucleation and growth in anthropogenic sulfur plumes, we have developed a model that incorporates TwO Moment Aerosol Sectional (TOMAS) (Adams and Seinfeld, 2002) microphysics into the System for Atmospheric Modelling (SAM; Kairoutdinov and Randall, 2003), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM)
Summary
It has been established that aerosols have a cooling effect on climate through the direct and indirect aerosol effects, but the magnitude of these effects is still very uncertain (Solomon et al, 2007). To better understand the number and size of particles that should be effectively emitted from anthropogenic sources in regional and global models, we explore the evolution of the number and size of sulfate aerosol particles inside coal-fired power-plant plumes using a 3-D fluid-dynamics model of plume chemistry and physics: the System for Atmospheric Modelling (Kairoutdinov and Randall, 2003) with TwO Moment Aerosol Sectional (Adams and Seinfeld, 2002) microphysics (SAM-TOMAS). This model uses a sub-km resolution to resolve the variation of chemistry and physics within the plumes. The total domain dimensions were 51.2 km × 24 km × 2 km for the 400 × 400 × 40 m grid-box cases, and 102.4 km × 48 km × 2 km for the 800 × 800 × 40 m grid-box cases
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