Research ArticleATMOSPHERIC SCIENCE

Climate models miss most of the coarse dust in the atmosphere

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Science Advances  08 Apr 2020:
Vol. 6, no. 15, eaaz9507
DOI: 10.1126/sciadv.aaz9507
  • Fig. 1 Constraints on the global coarse dust size distribution.

    (A) Constraint on the global dust size distribution obtained using measurements of atmospheric dust size distributions (red/pink) indicates that the atmosphere contains substantially more coarse dust than obtained in a recent analysis (black/gray; (16)) and accounted for in an ensemble of global model simulations (colored lines). Each size distribution is normalized such that the integral of dV/dD equals one. (B) Size-resolved log-mean bias against measurements of dust size distribution (see also Fig. 2) indicates that our constraints on the coarse dust size distribution perform better than those obtained from Kok et al. (16) (black/gray) and an ensemble of global model simulations (blue/cyan; global models used are shown in Fig. 1A). The last column shows the overall log-mean bias for all coarse dust between diameter 5 and 20 μm. The shading in (A) and the error bars in (B) represent the 95% confidence interval.

  • Fig. 2 Measurement compilation of coarse dust size distributions indicates that current global models substantially underestimate coarse dust fractions.

    We compare each measurement [purple dots; compiled by (18)] against the corresponding seasonally averaged dust size distribution obtained from an ensemble of model simulations (blue lines) as well as from this study (red lines). All size distributions are normalized at 5-μm diameter to emphasize the discrepancies.

  • Fig. 3 Constraints on the mass of dust in the atmosphere.

    (A) Size-resolved dust mass distribution (Tg) indicates that the mass of dust in the atmosphere (red/pink) is significantly more than those obtained from (16) (black/gray) or an ensemble of AeroCom models obtained from (19) (colored lines/cyan bars), and (B) shows the corresponding atmospheric dust load (Tg) integrated for the coarse dust (D = 5.0 to 20 μm), fine dust (D = 0.1 to 5.0 μm), and all dust (D = 0.1 to 20 μm). The shading in (A) and the error bars in (B) represent the 95% confidence interval.

  • Fig. 4 Constraints on dust direct radiative effects at the top of the atmosphere (DRETOA W·m−2).

    Size-aggregated DRETOA indicates that accounting for the missing coarse dust increases the coarse dust warming, resulting in an overall reduction in the global all-dust radiative cooling. The DRETOA (W·m−2) values are obtained in this study (red/pink), from Kok et al. (16) (black/gray), and an ensemble of AeroCom models (blue lines). (A) DRETOA values for the coarse dust (D = 5.0 to 20 μm), fine dust (D = 0.1 to 5.0 μm), and all dust (D = 0.1 to 20 μm). (B) All-dust DRETOA values for longwave (LW) and shortwave (SW) components and the net (LW + SW). The error bars represent the 95% confidence interval.

Supplementary Materials

  • Supplementary Materials

    Climate models miss most of the coarse dust in the atmosphere

    Adeyemi A. Adebiyi and Jasper F. Kok

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