Anthropogenic warming degrades spring air quality in Northeast Asia by enhancing atmospheric stability and transboundary transport

Abstract

Air pollutants can travel long distances from their sources, often causing severe particulate matter (PM) pollution in downwind regions. This transboundary pollution is largely influenced by meteorology and hence its changes associated with climate change. However, the effects of anthropogenic warming on transboundary pollution remain unclear. We show that springtime PM pollution can worsen with anthropogenic warming not only in the upwind region (northern China) but also in the downwind regions (South Korea and southern Japan). The worse air quality in northern China is attributed to a shallower boundary layer due to warmer air advection in the upper levels from high-latitude Eurasia and thus increased atmospheric stability. In the downwind regions, enhanced westerly/southwesterly anomalies induced by anthropogenic warming strengthen transboundary transport. The increase in primary aerosol concentrations due to the shallower boundary layer and/or enhanced transboundary transport is ~14% in northern China, ~13% in South Korea, and ~17% in southern Japan. The elevated relative humidity due to enhanced moisture transport by the wind anomalies promotes secondary aerosol formation, which further degrades the air quality in the downwind regions. The enhancement ratio of secondary aerosols relative to changes in primary aerosols is ~1 in northern China, ~1.12 in South Korea, and ~1.18 in southern Japan due to anthropogenic warming.