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. Mineral dust aerosols cool and warm the atmosphere byscattering and absorbing solar (shortwave: SW) and thermal (longwave: LW)radiation. However, significant uncertainties remain in dust radiativeeffects, largely due to differences in the dust size distribution andspectral optical properties simulated in Earth system models. Dust modelstypically underestimate the coarse dust load (more than 2.5 µm indiameter) and assume a spherical shape, which leads to an overestimate ofthe fine dust load (less than 2.5 µm) after the dust emissions in themodels are scaled to match observed dust aerosol optical depth at 550 nm(DAOD550). Here, we improve the simulated dust properties with data setsthat leverage measurements of size-resolved dust concentration, asphericityfactor, and refractive index in a coupled global chemical transport modelwith a radiative transfer module. After the adjustment of size-resolved dustconcentration and spectral optical properties, the global and annual averageof DAOD550 from the simulation increases from 0.023 to 0.029 and fallswithin the range of a semi-observationally based estimate (0.030 ± 0.005). The reduction of fine dust load after the adjustment leads to areduction of the SW cooling at the top of the atmosphere (TOA). To improveagreement against a semi-observationally based estimate of the radiativeeffect efficiency at TOA, we find that a less absorptive SW dust refractiveindex is required for coarser aspherical dust. Thus, only a minor differenceis estimated for the net global dust radiative effect at TOA (−0.08 vs.−0.00 W m−2 on a global scale). Conversely, our sensitivitysimulations reveal that the surface warming is substantially enhanced nearthe strong dust source regions (less cooling to −0.23 from −0.60 W m−2 on a global scale). Thus, less atmospheric radiativeheating is estimated near the major source regions (less heating to 0.15from 0.59 W m−2 on a global scale), because of enhanced LWwarming at the surface by the synergy of coarser size and aspherical shape.

Less atmospheric radiative heating by dust due to the synergy of coarser size and aspherical shape