The authors quantify the radiative effect of black carbon (BC) on simulated aerosol concentrations during the heavily polluted haze event of 11–14 January 2013 in northern China using the chemistry version of the Weather Research and Forecasting Model (WRF-Chem). As a result of the stable synoptic conditions, simulated concentrations of BC and PM2.5 averaged over the study period were about 8–16 μg m?3 and 80–100 μg m?3, respectively, in the control simulation (CTRL). When BC emissions were doubled (2BC), tripled (3BC), and quadrupled (4BC) relative to the CTRL run, the simulated concentrations of aerosols in different regions showed distinct changes. The radiative effect of BC was simulated to increase concentrations of aerosols over Tianjin (Dom1) and southern Henan (Dom3), but to decrease in southern Hebei (Dom2). Relative to the CTRL simulation, concentrations of PM2.5 over Dom1, Dom2, and Dom3 were simulated in 4BC to change by +18.6 μg m?3 (+32.3%), ?5.7 μg m?3 (?7.3%), and +7.2 μg m?3 (+12.6%), respectively. The BC-induced increases in aerosol concentrations corresponded mainly to the reductions in planetary boundary layer height over Dom1 and Dom3. The reductions of aerosol concentrations in Dom2 were mainly caused by the weakened wind convergence at 850 hPa and reduced concentrations of sulfate and nitrate associated with the reduced surface-layer ozone levels and relative humidity.