Preprints
https://doi.org/10.5194/acp-2021-134
https://doi.org/10.5194/acp-2021-134

  25 Feb 2021

25 Feb 2021

Review status: this preprint is currently under review for the journal ACP.

Less atmospheric radiative heating due to aspherical dust with coarser size

Akinori Ito1, Adeyemi A. Adebiyi2, Yue Huang2, and Jasper F. Kok2 Akinori Ito et al.
  • 1Yokohama Institute for Earth Sciences, JAMSTEC, Yokohama, Kanagawa, 236-0001, Japan
  • 2Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA

Abstract. Mineral dust aerosols cool and warm the atmosphere by scattering and absorbing both solar (short-wave: SW) and thermal (long-wave: LW) radiation. However, large uncertainties remain in dust radiative effects, largely due to differences in the dust size distribution and optical properties simulated in Earth system models. Here, 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). The global and annual average of dust aerosol optical depth at 550 nm (DAOD550) from the improved simulation (0.029) falls within the range of a semi-observation-based estimate (0.030 ± 0.005), in contrast to that (0.023) of the default simulation. Improved agreement against semi-observation-based estimate of the radiative effect efficiency was obtained using less absorptive SW and more absorptive LW dust refractive indices. Our sensitivity simulations reveal that the improved simulation leads to a similar net global dust radiative effect at the Top Of Atmosphere (TOA) on a global scale to the default simulation (−0.08 vs. −0.09 W ·m−2) but results in less cooling at the surface (−0.23 vs. −0.88 W ·m−2), because of enhanced LW warming by coarser aspherical dust. Our results thus suggest less atmospheric radiative heating due to aspherical dust with coarser size over the major source regions (0.15 vs. 0.79 W ·m−2 on a global scale).

Akinori Ito et al.

Status: open (until 22 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-134', Anonymous Referee #1, 13 Apr 2021 reply
  • RC2: 'Comment on acp-2021-134', Anonymous Referee #2, 18 Apr 2021 reply

Akinori Ito et al.

Akinori Ito et al.

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Short summary
We improve the simulated dust properties with datasets that leverage measurements of size-resolved dust concentration and particle shape. The improved simulation suggests much less atmospheric radiative heating over the major source regions, compared to the default simulation. The less intensified atmospheric heating due to mineral dust could substantially modify vertical temperature profile in Earth system models, and thus has important implications for the projection of dust feedback.
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