Abstract. The effect of black carbon (BC) on air quality and the climate is still unclear, which is partly because of the poor understanding regarding the BC aging process in the atmosphere. In this work, we developed a new approach to simulate the BC mixing state (i.e., other species coated on the BC surface) based on an emissions inventory and back-trajectory analysis. The model tracks the evolution of the BC aging degree (characterized by the ratio of the whole particle size and BC core) during atmospheric transport. Using the models, we quantified the mass-averaged aging degree of total BC particles transported to a receptor (e.g., an observation site) from various emission origins (i.e., 0.25° × 0.25° grids). The simulations showed good agreement with the field measurements, which validated our model calculation. Modeling the aging process of BC during atmospheric transport showed that it strongly dependent on emission levels. BC particles from extensive emission origins (i.e., polluted regions) were characterized by a higher aging degree during atmospheric transport due to more co-emitted coating precursors. On the other hand, high-emission regions also controlled the aging process of BC particles that were emitted from cleaner regions and passed through these polluted regions during atmospheric transport. The simulations identified the important roles of extensive emission regions in the BC aging process during atmospheric transport, implying the enhanced contributions of extensive emission regions to BC light absorption. This revealed that emission reductions in polluted regions could achieve more benefits for improving air pollution and climate change. Emission reductions in polluted regions not only decreased the aging degree of BC emitted from these regions but also reduced the aging process of BC emitted from other origins during atmospheric transport. Moreover, emissions reduction in polluted regions may be more efficient in counteract the suppression of planetary boundary layer (PBL) by BC particles (e.g., Zdunkowski et al., 1976; Jacobson, 1998; Wendisch et al., 2008; Barbaro et al., 2013; Ding et al., 2016; Wang et al., 2018), because a greater decrease in the BC aging degree during atmospheric transport would weaken the light absorption capability of BC in the upper PBL. The simulation of the BC aging degree during atmospheric transport provided more clues for improving air pollution and climate change.;
