Implementation of dust emission and chemistry into the Community Multiscale Air Quality modeling system and initial application to an Asian dust storm episode

Abstract

The US Environmental Protection Agency's (EPA) Community Multiscale Air Quality (CMAQ) modeling system version 4.7 is further developed to enhance its capability in simulating the photochemical cycles in the presence of dust particles. The new model treatments implemented in CMAQ v4.7 in this work include two online dust emission schemes (i.e., the Zender and Westphal schemes), nine dust-related heterogeneous reactions, an updated aerosol inorganic thermodynamic module ISORROPIA II with an explicit treatment of crustal species, and the interface between ISORROPIA II and the new dust treatments. The resulting improved CMAQ (referred to as CMAQ-Dust), offline-coupled with the Weather Research and Forecast model (WRF), is applied to the April 2001 dust storm episode over the trans-Pacific domain to examine the impact of new model treatments and understand associated uncertainties. WRF/CMAQ-Dust produces reasonable spatial distribution of dust emissions and captures the dust outbreak events, with the total dust emissions of ~111 and 223 Tg when using the Zender scheme with an erodible fraction of 0.5 and 1.0, respectively. The model system can reproduce well observed meteorological and chemical concentrations, with significant improvements for suspended particulate matter (PM), PM with aerodynamic diameter of 10 μm, and aerosol optical depth than the default CMAQ v4.7. The sensitivity studies show that the inclusion of crustal species reduces the concentration of PM with aerodynamic diameter of 2.5 μm (PM<sub>2.5</sub>) over polluted areas. The heterogeneous chemistry occurring on dust particles acts as a sink for some species (e.g., as a lower limit estimate, reducing O<sub>3</sub> by up to 3.8 ppb (~9%) and SO<sub>2</sub> by up to 0.3 ppb (~27%)) and as a source for some others (e.g., increasing fine-mode SO<sub>4</sub><sup>2−</sup> by up to 1.1 μg m<sup>−3</sup> (~12%) and PM<sub>2.5</sub> by up to 1.4 μg m<sup>−3</sup> (~3%)) over the domain. The long-range transport of Asian pollutants can enhance the surface concentrations of gases by up to 3% and aerosol species by up to 20% in the Western US

Effects of mineral dust on global atmospheric nitrate concentrations

“…The presence of mineral cations can also affect the aerosol ammonium concentrations due to thermodynamic interactions with the remainder ions in the aqueous phase (Karydis et al, 2010(Karydis et al, , 2011a. Furthermore, heterogeneous chemistry occurring on dust particles can also act as a source for sulfate (Wang et al, 2012).…”

“…The long-range transport of dust particles can influence the aerosol dynamics and atmospheric chemistry thousands of kilometers downwind of the source regions, while the chemical processing of the dust during transport can mobilize nutrients that are important for the marine biota (Solmon et al, 2009). Under favorable conditions, dust particles from the Sahara can travel across the Mediterranean Sea toward Europe (Mitsakou et al, 2008;Querol et al, 2009;Bangert et al, 2012) or across the Atlantic Ocean toward the Caribbean (Chiapello et al, 2005;Kallos et al, 2006) and South America (Formenti et al, 2001), while dust from the Gobi and Taklimakan deserts often crosses the Pacific and can reach the west coast of the Americas (Fairlie et al, 2010;Wang et al, 2012;Karydis et al, 2011b). The dust particles can substantially influence air quality (Giannadaki et al, 2014).…”

“…Several studies in the past have shown that the simulation of these effects, especially in areas where dust or sea salt comprises a significant portion of total particulate matter, can considerably improve model predictions (Dentener et al, 1996;Gong et al, 1997;Jacobson, 1999;Jacob, 2000;Song and Carmichael, 2001;Moya et al, 2002;Bian and Zender, 2003;Laskin et al, 2005;Hodzic et al, 2006;Kallos et al, 2007;Astitha and Kallos, 2009;Athanasopoulou et al, 2008Athanasopoulou et al, , 2010Fountoukis et al, 2009;Karydis et al, 2010Karydis et al, , 2011aTsyro et al, 2011;Wang et al, 2012;Im, 2013;Trump et al, 2015). According to their findings, including marine and crustal species in models can substantially affect the phase partitioning of nitrate aerosols.…”

Heterogeneous chemistry: a mechanism missing in current models to explain secondary inorganic aerosol formation during the January 2013 haze episode in North China

“…Field studies during haze days in China proposed that the large amount of sulfate and nitrate were more likely generated via heterogeneous chemistry than gas-phase and aqueous-phase chemistry Shao, 2009, 2010;Li et al, 2011;Wang et al, 2012cWang et al, , 2014cZhao et al, 2013b). Modeling studies have used 0-D to 3-D air quality models to research on the role of heterogeneous reactions in sulfate and nitrate formation on the surface of mineral particles (Zhang et al, 1994;Dentener et al, 1996;Zhang and Carmichael, 1999;Wang et al, 2012a). However, few studies have comprehensively evaluated the effect of heterogeneous chemistry on haze formation in China by using the 3-D models because of a lack of treatments for heterogeneous reactions in most climate and chemical transport models.…”

Heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with illite and Arizona test dust particles

“…After being mobilized, dust particles with a mass mean diameter of < 10 µm can stay in the troposphere for a few days and be transported over thousands of kilometres (Prospero, 1999;Fairlie et al, 2010). The heterogeneous reactions of mineral dust particles during transport can directly and/or indirectly impact the levels of many important trace gases, including NO x , O 3 , and HO x radicals (Dentener et al, 1996;de Reus et al, 2005;Wang et al, 2012;Zhu et al, 2010). In addition, the chemical aging of dust particles (e.g.…”