Application of turbulent diffusion term of aerosols in mesoscale model

The presence of unfavorable meteorological conditions triggers pollution, and then further weakens turbulence, especially in the stable boundary layer (SBL), which is a frequent situation in heavy pollution episodes in China. The inapplicability of the classical Monin-Obukhov similarity theory (MOST) and the uncertainty of the planetary boundary layer height can lead to large deviation of turbulent diffusion in the SBL in numerical simulations. However, in current mesoscale models, no term has been used to accurately describe the turbulent diffusion of aerosols. Therefore, we use the Mixing-Length theory to obtain the turbulent diffusion term of aerosols based on high-resolution observational data, and, for the first time, embed this term into a mesoscale model, which makes the turbulent diffusion process of aerosols more truly depicted. Results from a two-way coupled atmospheric-chemistry mesoscale model demonstrate that the turbulent diffusion term of aerosols can improve the problem of overestimated PM_2.5 concentration in Eastern China.