Direct radiative forcing of light-absorbing carbonaceous aerosol and the influencing factors over China

Abstract. Black carbon (BC) and brown carbon (BrC) are the dominant light-absorbing carbonaceous aerosols (LACs) that contribute significantly to climate change through absorbing and scattering radiation. We used GEOS-Chem integrated with the Rapid Radiative Transfer Model for General Circulation Models to estimate LAC properties and direct radiative forcings (DRFs) in China. Primary BrC (Pri-BrC) and secondary BrC (Sec-BrC) were separated from organic carbon and modeled as independent tracers. LAC Chinese anthropogenic emissions and refractive indexes were updated. Additionally, we investigated the impacts of LAC properties and atmospheric variables on LAC DRFs based on principal component analysis. It was shown that BC exerts a warming effect at the top of the atmosphere, while Pri-BrC and Sec-BrC induce a cooling effect. At the surface, they collectively lead to surface cooling, whereas within the atmosphere, they all can contribute to atmospheric heating, with 1.848 ± 1.098, 0.146 ± 0.079 and 0.022 ± 0.008 W m−2, respectively. The atmospheric shortwave DRFs of BC and Pri-BrC were proportional to their corresponding concentrations, aerosol optical depth (AOD) and absorption aerosol optical depth (AAOD), and they were inversely proportional to the single scattering albedo, surface albedo and ozone concentration in most regions. The surface longwave DRFs for the LACs showed negative correlations with water vapor in most areas. The highest atmospheric warming effect of LACs was observed in Central China, followed by East China, owing to the high LAC concentrations, AOD and AAOD as well as the low surface albedo and ozone concentration. This study enhances our understanding of the climatic impacts of LACs.