 The study investigates the impact of atmospheric aerosols on terrestrial gross primary productivity, GPP, using the Boreal Ecosystem Productivity Simulator, BEPS, over cropland and grassland ecosystems in North China. Results suggest that aerosols can reduce GPP of sunlit leaves by decreasing direct solar radiation, but increase GPP of shaded leaves by increasing diffuse solar radiation. The impact of aerosols on GPP is more significant over the cropland ecosystem with an AOD value of 0.3 to 0.6 and a diffuse fraction around 30 to 40 percent. The study improves the accuracy of GPP modelling using BEPS by highlighting the aerosol effect on GPP via solar radiation over highly polluted regions. This article was authored by Yaofeng, Dongmei Chen, and Xinijiao.