Impacts of plateau-induced lee troughs on regional PM2.5 over the Korean Peninsula

Abstract

Interactions between synoptic and local-scale meteorological factors can affect the transport and dispersion of air pollutants and increase PM2.5 concentrations in some regions, with serious implications for human health. We investigated the impacts of the highly elevated topography of the Kaema Plateau, a highland area in the northeastern part of the Korean Peninsula, on the development of a low-pressure systems (lee troughs) and its effects on PM2.5 behavior on the Korean Peninsula. The study involved three numerical modeling experiments in which the terrain height of the Kaema Plateau was changed to examine how PM2.5 dispersion and accumulation are affected by lee troughs resulting from the topography of the Kaema Plateau. Terrain height can affect the development of a low-pressure system, as well as its location in the downwind area. Our results show that the low-pressure systems (lee troughs) induced by the highly modified Kaema Plateau tend to increase the PM2.5 concentration in Gangneung, where the emission rate is low and decrease it in the Seoul metropolitan area. According to the Integrated Process Rate analysis, the reduced PM2.5 concentration in metropolitan Seoul was mainly caused by increased westerly winds induced by the developed low-pressure system. Conversely, PM2.5 concentrations increased in Gangneung because of the increased horizontal advection. The diffusion flux reached 37.0 μg m−3 from surrounding regions to Gangneung owing to the increased westerly winds. Overall, this study shows that the relationship between air quality and synoptic-scale meteorological conditions may differ depending on topographical characteristics, emission sources, and pollutant concentration distributions. It also provides guidance for future studies on the effects of lee troughs on meteorological conditions and air quality in the Korean Peninsula.