Changes in column aerosol optical depth and ground-level particulate matter concentration over East Asia

Abstract

Different spatio-temporal variations and trends in column aerosol optical depth (AOD) and surface particulate matter (PM10; diameter < 10 mu m) mass concentration were found for selected regions of East Asia. Enhanced AOD over North China and its downwind regions (Yellow Sea, Korea) occurred in June, compared with March-April over South China. Increased PM10 concentration in both North and South China was observed from late fall to spring. In Northeast China, a peak in AOD appeared during March, but high PM10 concentrations occurred in December-January. A significantly increasing trend in AOD was found in North and Northeast China, whereas surface PM10 concentrations over most megacities in these two regions declined almost linearly. This contradictory trend between AOD and PM10 concentration can be attributed to large emissions reductions in near-surface coarse particles, mainly accredited to a series of strict control measures. In other words, there has been no meaningful reduction in fine-mode particles including secondary aerosols. On the other hand, space-based CALIOP measurements revealed that approximately 60 similar to 70% (40 similar to 50%) of AOD was contributed by the aerosols present above 1 km (above 2 km) altitude. Our findings suggest that stronger emission controls for precursor gaseous emissions as well as submicron particles are required to decrease particulate air pollution, so as to further reduce their radiative forcing.