LAUSR

Abstract We study the regionally different impacts of aerosol direct radiative effects (DRE) by PM2.5 on the decrease in the solar radiation over South Korea (hereafter, Korea) for February 2015, using the WRF-CMAQ two-way modeling system. Two different numerical experiments were designed based on the on- and off-aerosol feedback option to evaluate the impact of aerosol DRE on the simulated meteorology and solar radiation. We find that the spatial pattern of the decrease in solar radiation does not agree with that of the PM2.5 concentrations. The largest decrease in solar radiation occurs around the southwest part of Korea (G1), where much lower PM2.5 concentrations appear, compared to other inland regions (G2). The investigation of the chemical species that constitute PM2.5 reveals that the G1 sites have a relatively higher fraction of sulfate (S/PM2.5) than the G2 sites. This finding reveals that the higher sulfate loading over Korea could lead to the larger aerosol DRE. The high sulfate loading, which mainly appeared in the southwest part of Korea, was identified as not only originating from national local emission sources, but also from the long-range transport (LRT) of sulfate and its precursors. Overall, the regionally different distributions of aerosol DRE, especially for solar radiation in Korea, can be attributed partly to the different contributions of the chemical species that constitute PM2.5, particularly sulfate.