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

Abstract

[1] A six-moment microphysics module for sulfate aerosols based on the quadrature method of moments has been incorporated in a host 3-D regional model, the Multiscale Air Quality Simulation Platform. Model performance was examined and evaluated by comparison with in situ observations over the eastern United States for a 40-day period from 19 July to 28 August 1995. The model generally reproduces the spatial patterns (sulfate mixing ratios and wet deposition) over the eastern United States and time series variations of sulfate mass concentrations. The model successfully captured the observed size distribution in the accumulation mode (radius 0.1-0.5 mm), in which the sulfate is predominately located, while underestimating the nucleation and coarse modes on the basis of the size distributions retrieved from the modeled six moments at the Great Smoky Mountains (GSM). This is consistent with better model performance on the effective radius (ratio of third to second moment, important for light scattering) than on numbermean and mass-mean radii. However, the model did not predict some of the moments well, especially the higher moments and during the dust events. Aerosol components other than sulfate such as dust and organics appear to have contributed substantially to the observed aerosol loading at GSM. The model underpredicted sulfate mixing ratios by 13% with about 50% of observations simulated to within a factor of 2. One of the reasons for this underestimation may be overprediction of sulfate wet deposition. Sulfate mass concentrations and number concentrations were high in the source-rich Ohio River valley, but number concentrations were also high over the mid-Atlantic coast (New Jersey area). Most (77%) sulfate amount was below 2.6 km, whereas most sulfate number (>52%) was above 2.6 km except over Ohio River valley (41%). These results demonstrate the accuracy, utility, practicality, and efficiency of moment-based methods for representing aerosol microphysical processes in large-scale chemical transport models.

Online coupled regional meteorology chemistry models in Europe: current status and prospects

“…The third method, called the moment approach, is similar to the modal approach but is more general since the size distribution can have an arbitrary shape and does not need to be log-normal. Rather, the distribution is described with several moments, and the evolution of the moments is predicted by the model (Yu et al, 2003).…”

“…American, Canadian and Japanese institutions have developed and used online coupled models operationally for AQ forecasting and for research (GATOR-MMTD: Jacobson et al, 1996, 1997aWRF-Chem: Grell et al, 2005; GEM-AQ: Kaminski et al, 2007;WRF-CMAQ: Mathur et al, 2008;Yu et al, 2011;GEM-MACH: Moran et al, 2010). The European Centre for Medium Range Weather Forecasting (ECMWF) also noted the relevance of online chemistry (Hollingsworth et al, 2008) and several national weather services (such as DMI, UK MetOffice) and research institutions (such as KIT, ISAC, UniHH) are developing online models.…”

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

“…According to this approach, aerosol size distributions are approximated using statistical moments with idealized properties (Whitby, 1981;Whitby and McMury, 1997;McGraw, 1997;Ackermann et al, 1998;Wilson et al, 2001;Wright et al, 2001;Yu et al, 2003). Typically, a number of overlapping log-normally distributed modes are assumed to account for different types of aerosols.…”

Aerosol indirect effect on the grid-scale clouds in the two-way coupled WRF–CMAQ: model description, development, evaluation and regional analysis

“…The size distribution of aerosols in tropospheric air quality models can be represented by the sectional approach (Zhang et al, 2002, the moment approach (Yu et al, 2003), and the modal approach (Binkowski and Roselle, 2003). In the aerosol module of CMAQ, the aerosol distribution is modeled as a superposition of three lognormal modes that correspond nominally to the ultrafine (diameter (D p ) < 0.1 µm), fine (0.1 µm < D p < 2.5 µm), and coarse (D p > 2.5 µm) particle size ranges.…”