Effects of atmospheric aerosols on terrestrial carbon fluxes and CO2 concentrations in China

Atmospheric aerosols have contributed to the terrestrial carbon cycle through diffuse radiation fertilization effect and hydrometeorological feedbacks. Subsequently, perturbations in terrestrial carbon sink alter atmospheric carbon dioxide (CO2) concentrations and influence future climate change. Here, we use a regional climate model, RegCM4, coupled with the Yale Interactive terrestrial Biosphere model (YIBs) to assess the effects of the current aerosol loading on terrestrial carbon fluxes and atmospheric CO2 concentrations during 2006-2015 over China. We found that aerosols enhance gross primary production (GPP) by 0.36 Pg C yr(-1) (5%), which primarily stems from Southwest and Southeast China. Meanwhile, the aerosol-induced diffuse fraction (DF) increase, surface cooling and vapor pressure deficit (VPD) decrease together lead to a - 0.06 Pg C yr(-1) (21%) reduction in the net ecosystem exchange (NEE). Among them, aerosol-induced DF increment is found to be the dominant contributor, which covers similar to 59-62% of China's land area. The effects of aerosols on GPP and NEE are more evident in the growing season, with maximum effects occurring in July and August, respectively. Moreover, the terrestrial carbon sink enhancement due to aerosols further results in a significant decline in CO2 concentrations, with a large reduction (> 2 ppm) found in southern and eastern parts of China during the summer. Our results highlight the importance of understanding the interactions among aerosol pollution, climate change, and the global carbon cycle.