[A-CG35] Projection and detection of global environmental change

[ACG35-03] Implication of aspherical coarse dust on aerosol radiative effect

*Akinori Ito¹, Adeyemi A. Adebiyi², Yue Huang², Jasper F. Kok² (1.Japan Agency for Marine-Earth Science and Technology, 2.University of California)

Keywords:Aerosol, Earth system model, Radiative effect

Mineral dust aerosols cool and warm the atmosphere by scattering and absorbing both short-wave (SW) and long-wave (LW) radiation. However, large uncertainties remain in dust radiative effects, largely due to differences in the dust size distribution and abundance simulated in Earth system models. We improve the simulated dust properties with datasets that leverage measurements of size-resolved dust concentration and asphericity factor (improved simulation) in a coupled global chemical transport model (IMPACT) with a radiative transfer module (RRTMG) (default simulation).
Global and annual average of dust aerosol optical depth at 550 nm (DAOD₅₅₀) from the improved simulation falls within the range in semi-observation-based estimate, in contrast to that from default simulations. We then use the model to perform different numerical experiments to investigate the sensitivity of the dust radiative effect to the refractive index. A better agreement was obtained with the less absorptive SW and the more absorptive LW dust refractive indices against semi-observation-based estimate of the radiative effect efficiency. Our sensitivity simulations reveal that the improved simulation leads to a similar net dust radiative effect at the Top Of Atmosphere (TOA) on a global scale to the default simulation but results in less cooling at the surface, because of enhanced LW warming. Our results thus suggest less atmospheric radiative heating due to aspherical dust with coarser size over the major source regions.