资源环境科技发展态势分析平台

Direct Aerosol Radiative Forcing (DARF) characterizes aerosol influences on the radiative energy budget due to scattering and absorption of solar radiation, while clear uncertainties remain in both global and regional DARF estimations due to differences on aerosol properties and time periods considered. Through a multi-source strategy, this study systematically investigates the DARFs over Beijing, China, between 2001 and 2020. Ground-based observations from AERONET are used as “references”, and two satellite-based datasets (MODIS and MISR), atmospheric reanalysis (MERRA-2) and numerical modelling (WRF-CMAQ) are considered. We unify the numerical simulations for DARF to ensure an fair intercomparison among difference datasets. Fortunately, the aerosol amount at the AERONET locations in Beijing can well represent those over the entire city regon, and the average DARF at the top of the atmosphere (TOA) in the past twenty years is found to be ~ −36 W/m² in Beijing. The relative differences in DARFs among different sources range between approximately −40% and 10%, and those in DARF efficiencies (DARFEs) are in a similar range (besides AERONET and MISR). The correlation coefficients on DARF between the AERONET and MERRA-2 results are found to be approxiamtely ~0.75, and both MODIS and MISR result in correlation coefficients with AERONET over 0.80. However, the agreement at the MISR TOA DARF is caused by smaller AOD and larger DARFE. The DARF uncertainties based on AERONET, MODIS and MISR range from approximately 10% to over 20%. For the numerical simulations, the WRF-CMAQ results agree reasonably with the observation-based results, while their DARF magnitudes are merely about one-third of those from observation-based results. Clear differences among DARFs given by datasets of different kinds indicate that the uncertainties on aerosol direct forcings cannot be neglected, and that more efforts are still needed to unify and to improve our understanding on it.