Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

• Published in: Atmospheric chemistry and physics Vol. 12; no. 24; pp. 11833 - 11856
• Main Authors: Kajino, M, Inomata, Y, Sato, K, Ueda, H, Han, Z, An, J, Katata, G, Deushi, M, Maki, T, Oshima, N, Kurokawa, J, Ohara, T, Takami, A, Hatakeyama, S
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 17.12.2012; Copernicus Publications
• Subjects: Aerosols; AGR; Air quality; Analysis; Asian; Atmospheric physics; Categories; Computer simulation; Marine; Mathematical models; Optical properties; Transport
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-12-11833-2012

A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2), was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super- mu m. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK), soot-free particles in the accumulation mode (ACM), soot aggregates (AGR), and particles in the coarse mode (COR). The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation ( Delta x = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM sub(1)/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non-sea-salt SO sub(4) super(2-) mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO sub(4) super(2-) was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO sub(3) super(-) was mixed with sea salt at Hedo, whereas 53.7% of the NO sub(3) super(-) was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO sub(3) onto sea salt particles during transport over the ocean accounts for the difference in the NO sub(3) super(-) mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.