Evaluation of dust and trace metal estimates from the Community Multiscale Air Quality (CMAQ) model version 5.0

Abstract

The Community Multiscale Air Quality (CMAQ) model is a state-of-the-science air quality model that simulates the emission, transformation, transport, and fate of the many different air pollutant species that comprise particulate matter (PM), including dust (or soil). The CMAQ model version 5.0 (CMAQv5.0) has several enhancements over the previous version of the model for estimating the emission and transport of dust, including the ability to track the specific elemental constituents of dust and have the model-derived concentrations of those elements participate in chemistry. The latest version of the model also includes a parameterization to estimate emissions of dust due to wind action. The CMAQv5.0 modeling system was used to simulate the entire year 2006 for the continental United States, and the model estimates were evaluated against daily surface-based measurements from several air quality networks. The CMAQ modeling system overall did well replicating the observed soil concentrations in the western United States (mean bias generally around ±0.5 μg m^−3); however, the model consistently overestimated the observed soil concentrations in the eastern United States (mean bias generally between 0.5–1.5 μg m^−3), regardless of season. The performance of the individual trace metals was highly dependent on the network, species, and season, with relatively small biases for Fe, Al, Si, and Ti throughout the year at the Interagency Monitoring of Protected Visual Environments (IMPROVE) sites, while Ca, K, and Mn were overestimated and Mg underestimated. For the urban Chemical Speciation Network (CSN) sites, Fe, Mg, and Mn, while overestimated, had comparatively better performance throughout the year than the other trace metals, which were consistently overestimated, including very large overestimations of Al (380%), Ti (370%) and Si (470%) in the fall. An underestimation of nighttime mixing in the urban areas appears to contribute to the overestimation of trace metals. Removing the anthropogenic fugitive dust (AFD) emissions and the effects of wind-blown dust (WBD) lowered the model soil concentrations. However, even with both AFD emissions and WBD effects removed, soil concentrations were still often overestimated, suggesting that there are other sources of errors in the modeling system that contribute to the overestimation of soil components. Efforts are underway to improve both the nighttime mixing in urban areas and the spatial and temporal distribution of dust-related emission sources in the emissions inventory

Assessment of long-term WRF–CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

“…Likewise, the model also used a comprehensive emission data set (Xing et al, 2015) which included aerosol precursors and primary particulate matter. Additional details on the aerosol speciation represented in the CMAQ model can be found in Carlton et al (2010), Foley et al (2010), and Appel et al (2013). Furthermore, Gan et al (2014b) discuss how the optical properties and AOD are estimated based on the predicted spatially and temporally varying compositional characteristics which included the full suite of inorganic and organic constituents.…”

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

“…The aerosol module in CMAQ is described by Binkowski and Roselle (2003), and updates are described by Bhave et al (2004), Yu et al (2007a), Carlton et al (2010), Foley et al (2010), and Appel et al (2013). 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).…”

Multi-year downscaling application of two-way coupled WRF v3.4 and CMAQ v5.0.2 over east Asia for regional climate and air quality modeling: model evaluation and aerosol direct effects

“…The WRF model configuration included the Morrison doublemoment scheme (Morrison et al, 2009), version 2 of the Kain-Fritsch cumulus scheme (Kain, 2004), the Asymmetric Convective Model version 2 (ACM2) planetary boundary layer (PBL) scheme (Pleim, 2007), the Pleim-Xiu land surface model (Xiu and Pleim, 2001), and the RRTMG shortwave and longwave radiation scheme (Iacono et al, 2008). The CMAQ model was configured using the Carbon Bond 2005 (CB05) chemical mechanism (Yarwood et al, 2005;Whitten et al, 2010) and the sixth-generation CMAQ aerosol module (AERO6) (Appel et al, 2013 (Gantt et al, 2014;He at al., 2015a, b;Glotfelty et al, 2017a, b;Glotfelty and Zhang, 2017) (Appel et al, 2013) using a horizontal resolution of 36 km covered most of China and parts of east Asia. The two-way coupled WRF-CMAQ used the same vertical resolution for WRF and CMAQ, i.e., 23σ layers from the surface to 100 hPa.…”