Regional and Sectoral Sources for Black Carbon Over South China in Spring and Their Sensitivity to East Asian Summer Monsoon Onset

Besides local emissions, biomass burning (BB) emissions in peninsula Southeast Asia (PSEA) and domestic anthropogenic emissions in North China (NC) are also significant black carbon (BC) sources over South China (SC) in spring. Meanwhile, the East Asian summer monsoon (EASM) is established with the wind field reversal, influencing the region-based contributions to BC over SC. Herein, BC sources for SC were tracked by region and by sector using the Community Earth System Model with a BC-tagging technique. During the spring of 2000-2014, 27% of BC surface concentration (BCS) and 64% of BC column burden (BCC) over SC stems from nonlocal sources. BC from NC is mainly transported below 850 hPa. It is the dominant nonlocal contribution to BCS (17%) and largely composed of residential and industrial sectors. Nonlocal emissions inside and outside China contribute 28% and 36% to BCC, respectively. Generally transported above 850 hPa, BC from PSEA is the largest nonlocal contributor (20%) to BCC and contributes 80% of BCC in BB sector. Additionally, the interannual variation in EASM onset times bring a maximum of -5% to +7%/-2% to +7% variation in BCC/BCS. The BC outflow/inflow contributed from NC dominates the BC decrease/increase over SC with southerly/northerly wind anomaly induced by early/late EASM onset, yet regional transport from PSEA contributes minor BC changes. The simulated BC is significantly positively correlated with the varying EASM onset times, but not with emissions, indicating the decisive role of meteorology in the interannual variation of BC over SC during springtime.