Optical Properties and Direct Radiative Effects of Aerosol Species at Global Scale Based on the Synergistic Use of MERRA-2 Optical Properties and the Forth Radiative Transfer Model

The overarching goal of the current study is to quantify the aerosol-induced clear-sky direct radiative effects (DREs) within the Earth-atmosphere system at the global scale and for the 40-year period 1980–2019. To this aim, the MERRA-2 aerosol radiative properties, along with meteorological fields and surface albedo, are used as inputs to the Foundation for Research and Technology-Hellas (FORTH) radiative transfer model (RTM). Our preliminary results, representative for the year 2015, reveal strong surface radiative cooling (down to −45 Wm−2) over areas where high aerosol loadings and absorbing particles (i.e., dust and biomass burning) dominate. This reduction of the incoming solar radiation in the aforementioned regions is largely attributed to its absorption by the overlying suspended particles resulting in atmospheric warming reaching up to 40 Wm−2. At the top of the atmosphere (TOA), negative DREs (planetary cooling) are computed worldwide (down to −20 Wm−2) with few exceptions over bright surfaces (warming up to 5 Wm−2). Finally, the strong variations between the obtained DREs of different aerosol species (dust, sea salt, sulfate, and organic/black carbon) as well as between hemispheres and surface types (i.e., land vs. ocean) are also discussed.