Size- and Composition-Resolved Externally Mixed Aerosol Model

Abstract

ABSTRACT. The need for a numerical algorithm to predict the growth of external mixtures of aerosol populations is common to several current areas of study, including aerosol radiative effects, particle production processes, and pollution source apportionment. This work describes a model that solves this problem for explicit external and internal mixtures for the processes of coagulation, condensation, deposition, activation, and nucleation. The solution is numerically accurate for both particulate mass and number conservation by virtue of a dual-moment sectional method for solute growth. In addition, evaporable components are calculated in moving sections to retain information during particle activation in supersaturated conditions. The model is illustrated by application to the problem of cloud processing in a marine boundary layer capped with a layer of stratus clouds. The aerosol population is tracked in an air parcel circulating within the boundary layer and through the cloud layer. Boundary layer structure and cloud supersaturation profiles are predicted from gradients of observed thermodynamic variables. The model shows the differential growth of particles during cloud processing in two different types of particle populations, one of sea-salt origin and the other of sulfate origin.

Modelling sea salt aerosol and its direct and indirect effects on climate

“…Aerosol size distributions are commonly approximated based on the bin approach, also often called "sectional" or "discrete" approach (Gelbard and Seinfeld, 1980;Warren and Seinfeld, 1985;Gelbard, 1990;Jacobson, 1997;Lurmann et al, 1997;Russell and Seinfeld, 1998;Meng et al, 1998;von Salzen and Schlünzen, 1999;Pilinis et al, 2000;Gong et al, 2003;Ma and von Salzen, 2006). According to the bin approach, a range of particle sizes is subdivided into a number of bins, or sections, with discrete values of the size distribution in each bin.…”

Moment‐based simulation of microphysical properties of sulfate aerosols in the eastern United States: Model description, evaluation, and regional analysis

“…The moments evolve solely by evolution of the abscissas with the weights remaining constant under condensation growth, and by evolution of the weights with the abscissas remaining constant under dry deposition [McGraw and Wright, 2003]. The condensation rate is the modified Fuchs-Sutugin formula [Russell and Seinfeld, 1998;Kreidenweis et al, 1991], and the Fuchs kernel [Fuchs, 1964;Jacobson et al, 1994] for coagulation is used. Dry deposition velocities have been calculated from the model of Giorgi [1986] for deposition to both ocean and land surfaces.…”

“…It is therefore necessary to include a microphysical representation of aerosol formation, evolution, and removal processes in atmospheric CTMs. Most previous approaches to aerosol microphysical modeling have simulated the particle distribution function (PDF) either explicitly, by a bin-sectional approach [Whitby and McMurry, 1997;Russell and Seinfeld, 1998;Von Salzen et al, 2000;Jacobson, 2002] or by a multimodal approach [Whitby and McMurry, 1997;Binkowski and Shankar, 1995;Wilson et al, 2001], in which particle size distributions are represented as the superposition of three lognormal subdistributions, or modes.…”

“…As noted by Benkovitz and Schwartz [1997], departure of modeled and observed values may not be attributed entirely to performance of the model because the observed values at a station are not necessarily representative of the grid cell as a whole and may be not suitable for evaluation of the model, which means to represent the mean values over the grid cell. In addition to the problem of the representativeness of the observations at a single location for the grid cell as a whole, the discrepancy between the modeled and observed wet deposition can be due to inaccuracy in the representation of locations and amounts of precipitation in the meteorological forecast model (here, MM5) that drives the chemical transport model and in the representation of wet removal processes [Seaman, 2000]. Discrepancies between model and observations might be due also to errors in boundary conditions, especially near the western edge of the model domain.…”

Modal Bin Hybrid Model: A surface area consistent, triple‐moment sectional method for use in process‐oriented modeling of atmospheric aerosols

“…Aerosol modeling approaches now range from the one-dimensional size-resolving modal or sectional approach (conventional internal mixture assumption in regional chemical transport models), the category approach (conventional external mixture assumption in global climate models), and the category approach with a few mixing state categories [Wilson et al, 2001;Vignati et al, 2004;Stier et al, 2005;Wang et al, 2009;Aquila et al, 2011;Kajino and Kondo, 2011;Liu et al, 2012;Kajino et al, 2012aKajino et al, , 2012b to the computationally expensive two-dimensional (size and mixing state) mixing state resolving approach [Russell and Seinfeld, 1998;Jacobson, 2001;Oshima et al, 2009;Matsui et al, 2013], the multiple category with mixing state resolving approach [Jacobson, 2001;Bauer et al, 2008;Bergman et al, 2012], and ultimately to the particleresolving approach [Riemer et al, 2009;Zaveri et al, 2010].…”