Impact of Collection Efficiency Associated with Microscale Surface Characteristics on Aerosol Dry Deposition and PM2.5 over East Asia

Aerosol dry deposition is an important sink of atmospheric particles, but its representation in chemical transport models remains uncertain. In particular, conventional parameterizations often neglect collection efficiency associated with microscale surface characteristics, which can strongly affect particle capture by surfaces. This study investigates how this process influences aerosol dry deposition and PM_2.5 over East Asia. Tower-based measurements of aerosol dry deposition velocity were used to evaluate model performance. Simulations without the enhanced collection efficiency substantially underestimated aerosol dry deposition velocity, by more than one order of magnitude relative to observations. This is consistent with previous studies reporting that the model underestimated observed deposition velocities for particles in the 0.2–2.0 μm size range by one to two orders of magnitude over forested regions. To address this discrepancy, collection efficiency associated with microscale surface characteristics was incorporated into the aerosol dry deposition framework, and its effects on regional PM_2.5 simulations over East Asia were evaluated across different land-use types and seasonal conditions. The updated representation increased aerosol dry deposition velocity and enhanced particle removal at the surface, leading to lower PM_2.5 concentrations over parts of East Asia. These results demonstrate that collection efficiency associated with microscale surface characteristics plays a critical role in aerosol dry deposition and can substantially affect regional PM_2.5 simulations. These findings highlight the need to refine aerosol deposition parameterizations to improve air quality predictions and reduce uncertainty in assessments.

 

Acknowledgment: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. RS-2025-16070879).