Aerosol absorption in global models from AeroCom phase III

Abstract. Aerosol-induced absorption of shortwave radiation can modify the climate through local atmospheric heating, which affects lapse rates, precipitation, and cloud formation. Presently, total amount aerosol is poorly constrained, main absorbing species (black carbon (BC), organic aerosols (OA), mineral dust) are diversely quantified in global models. As part third phase Aerosol Comparisons between Observations Models (AeroCom) intercomparison initiative (AeroCom III), we here document distribution magnitude current models quantify sources intermodel spread, highlighting difficulties attributing to different species. In total, 15 have provided present-day at 550 nm (using year 2010 emissions), 11 per The multi-model annual mean optical depth (AAOD) 0.0054 (0.0020 0.0098; nm), with range given as minimum maximum model values. This 28 % higher compared 0.0042 (0.0021 0.0076) AeroCom II 2000 but difference within 1 standard deviation, which, this study, 0.0023 (0.0019 Phase II). Of summed component AAOD, 60 (range 36 %–84 %) estimated be due BC, 31 (12 %–49 dust, (0 %–24 OA; however, components not independent terms their efficiency. internal mixtures aerosols, a major challenge lack common simple method attribute Therefore, when possible, internally mixed present study performed simulations using same for estimating OA, namely by removing it comparing runs without We discuss challenges species; compare burden, refractive indices, density; contrast mixing external mixing. BC mass coefficient (MAC) value 10.1 (3.1 17.7) m2 g−1 (550 AAOD 0.0030 (0.0007 0.0077). lifetime (and burden) explains much spread MAC spectral dependency striking. Several an Ångstrøm exponent (AAE) close 1, likely too low knowledge properties. Most do account brown underestimate OA.