EMTACS: Development and regional-scale simulation of a size, chemical, mixing type, and soot shape resolved atmospheric particle model

A new aerosol chemical transport model, the Eulerian Multiscale Tropospheric Aerosol Chemistry and dynamics Simulator (EMTACS) has been developed. This model resolves aerosol chemical composition, size distribution, mixing types, and shapes of fractal agglomerates in the atmosphere. These parameters are critical for accurate estimation of the hygroscopicity and optical properties of aerosols. The model implements a new aerosol dynamics module (Modal Aerosol Dynamics model for multiple Modes and fractal Shapes (MADMS)), which for the first time enables simulation of intermodal Brownian coagulation between two modes with very different size distributions using the modal moment approach. MADMS simulates Brownian coagulation for arbitrary fractal dimensions. Coagulation processes due to turbulence and sedimentation are also considered. The EMTACS model successfully reproduced the fractions of PM2.5 to PM10 of major inorganic aerosol components measured at Jeju Island in Korea in the spring of 2005 during the Atmospheric Brown Cloud-East Asian Regional Experiment 2005 (ABC-EAREX) campaign. The results indicate the capability of the model in interpreting the observed size distribution and mixing types of aerosol inorganic components. The spatial and temporal distribution of mixing types of inorganic components (nss-SO42-, NO3-, and NH4+) during long-range transport in East Asia is also discussed.