Comparison of three aerosol representations of NHM-Chem (v1.0) for the simulations of air quality and climate-relevant variables

• Published in: Geoscientific Model Development 2021-04, Vol.14 (4), p.2235-2264
• Main Authors: Kajino, Mizuo, Deushi, Makoto, Sekiyama, Tsuyoshi Thomas, Oshima, Naga, Yumimoto, Keiya, Tanaka, Taichu Yasumichi, Ching, Joseph, Hashimoto, Akihiro, Yamamoto, Tetsuya, Ikegami, Masaaki, Kamada, Akane, Miyashita, Makoto, Inomata, Yayoi, Shima, Shin-ichiro, Khatri, Pradeep, Shimizu, Atsushi, Irie, Hitoshi, Adachi, Kouji, Zaizen, Yuji, Igarashi, Yasuhito, Ueda, Hiromasa, Maki, Takashi, Mikami, Masao
• Format: Article
• Language: English
• Subjects: Accumulation; Aerosol dynamics; Aerosol light absorption; Aerosol-cloud interactions; Aerosols; Air; Air pollution; Air quality; Air quality forecasting; Air quality models; Atmospheric aerosols; Atmospheric particulates; Chemical speciation; Chemistry; Cloud condensation nuclei; Clouds; Comparative analysis; Condensation nuclei; Dust; Dust storms; Efficiency; Electromagnetic absorption; Equilibrium; Errors; Gas absorption; Hazardous materials; Hygroscopicity; Ice nucleation; Ice nuclei; Mathematical models; Meteorology; Methods; Nuclear accidents & safety; Nucleation; Nucleus; Optical properties; Optical thickness; Particle size distribution; Particulate matter; Pollutants; Precipitation; R&D; Radiation; Radiation-cloud interactions; Representations; Research & development; Salt particles; Salts; Scavenging; Sea salt particles; Simulation; Size distribution; Soot; Three dimensional models
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-14-2235-2021

This study provides comparisons of aerosol representation methods incorporated into a regional-scale nonhydrostatic meteorology–chemistry model (NHM-Chem). Three options for aerosol representations are currently available: the five-category non-equilibrium (Aitken, soot-free accumulation, soot-containing accumulation, dust, and sea salt), three-category non-equilibrium (Aitken, accumulation, and coarse), and bulk equilibrium (submicron, dust, and sea salt) methods. The three-category method is widely used in three-dimensional air quality models. The five-category method, the standard method of NHM-Chem, is an extensional development of the three-category method and provides improved predictions of variables relating to aerosol–cloud–radiation interaction processes by implementing separate treatments of light absorber and ice nuclei particles, namely, soot and dust, from the accumulation- and coarse-mode categories (implementation of aerosol feedback processes to NHM-Chem is still ongoing, though). The bulk equilibrium method was developed for operational air quality forecasting with simple aerosol dynamics representations. The total CPU times of the five-category and three-category methods were 91 % and 44 % greater than that of the bulk method, respectively. The bulk equilibrium method was shown to be eligible for operational forecast purposes, namely, the surface mass concentrations of air pollutants such as O3, mineral dust, and PM2.5. The simulated surface concentrations and depositions of bulk chemical species of the three-category method were not significantly different from those of the five-category method. However, the internal mixture assumption of soot/soot-free and dust/sea salt particles in the three-category method resulted in significant differences in the size distribution and hygroscopicity of the particles. The unrealistic dust/sea salt complete mixture of the three-category method induced significant errors in the prediction of the mineral dust-containing cloud condensation nuclei (CCN), which alters heterogeneous ice nucleation in cold rain processes. The overestimation of soot hygroscopicity by the three-category method induced errors in the BC-containing CCN, BC deposition, and light-absorbing aerosol optical thickness (AAOT). Nevertheless, the difference in AAOT was less pronounced with the three-category method because the overestimation of the absorption enhancement was compensated by the overestimation of hygroscopic growth and th