Retrieval of gridded aerosol direct radiative forcing based on multiplatform datasets
Abstract. Atmospheric aerosols play a crucial role in regional radiative
budgets. Previous studies on clear-sky aerosol direct radiative forcing
(ADRF) have mainly been limited to site-scale observations or model
simulations for short-term cases, and long-term distributions of ADRF in
China have not been portrayed yet. In this study, an accurate fine-resolution
ADRF estimate at the surface was proposed. Multiplatform datasets, including
satellite (MODIS aboard Terra and Aqua) and reanalysis datasets, served as
inputs to the Santa Barbara Discrete Atmospheric Radiative Transfer (SBDART)
model for ADRF simulation with consideration of the aerosol vertical profile
over eastern China during 2000–2016. Specifically, single-scattering albedo
(SSA) from the Modern-Era Retrospective Analysis for Research and
Application, Version 2 (MERRA-2) was validated with sun photometers over eastern
China. The gridded asymmetry parameter (ASY) was then simulated by matching
the calculated top-of-atmosphere (TOA) radiative fluxes from the radiative
transfer model with satellite observations (Clouds and the Earth's Radiant
Energy System, CERES). The high correlation and small discrepancy (6–8 W m −2 ) between simulated and observed radiative fluxes at three sites
(Baoshan, Fuzhou, and Yong'an) indicated that ADRF retrieval is feasible and
has high accuracy over eastern China. Then this method was applied in each grid
of eastern China, and the overall picture of ADRF distributions over eastern China
during 2000–2016 was displayed. ADRF ranges from −220 to −20  W m −2 , and
annual mean ADRF is −100.21  W m −2 , implying that aerosols have a strong
cooling effect at the surface in eastern China. With the economic development
and rapid urbanization, the spatiotemporal changes of ADRF during the past 17 years are mainly attributed to the changes of anthropogenic emissions in
eastern China. Our method provides the long-term ADRF distribution over eastern
China for the first time, highlighting the importance of aerosol radiative
impact under climate change.