Spatiotemporal variations and relationships of aerosol-radiation-ecosystem productivity over China during 2001-2014

Several air pollution episodes occurred in China in the past decade, and high levels of aerosols load also caused the changes of radiation, which could further influence the gross primary productivity (GPP) in the terrestrial ecosystem. This paper focuses on the spatiotemporal variations and relationship of aerosol-radiation-GPP in China during a heavy pollution period (2001-2014). For this purpose, the Fu-Liou radiation transfer mechanism model was used to estimate total radiation (TR) and diffuse radiation (DIFR) at the spatial resolution of 1° × 1° based on the satellite aerosol optical depth (AOD) and other auxiliary data. This model shows excellent performance with an R² of 0.88 and 0.79 for TR and DIFR, respectively. A significant increasing trend (0.23 W m^-2 year^-1) in TR was found in China in this phase, and it was mainly attributed to DIFR. Furthermore, a scenario without aerosols (AOD = 0) was simulated as a comparison to quantify the aerosol radiative forcing, which indicated that aerosols play a catalytic role in DIFR, increasing it by approximately 19.55%. Despite all this, aerosols have weakened the brightening of China due to the negative forcing on direct radiation. Meanwhile, 0.65-4.20 kgC m^-2 year^-1 increase of GPP was also captured in seven regions of China during this phase.However, the significant negative response of GPP to aerosol was found in most ecosystems in the growing season of vegetation, and the highest correlation of -0.76 (p < .01) existed in the central China forest regions. It suggests although aerosol causes a diffuse fertilization effect, GPP is still lost due to high levels of aerosol load in most areas of China during growing season of vegetation. This paper aims to determine the relationship among the aerosol-radiation-ecosystem productivity in different regions of China, which could provide a reference for the divisional strategy formulation and classification management in different ecosystems.