Atmospheric mean mineral aerosol abundance and direct radiative effect by dust for models and cases described in Li et al. (2020)
Li, Longlei; Mahowald, Natalie M.; Miller, Ron L.; García-Pando, Carlos Pérez; Klose, Martina; Hamilton, Douglas S.; Ageitos, Maria Gonçalves; Ginoux, Paul; Balkanski, Yves; Green, Robert O.; Kalashnikova, Olga; Kok, Jasper F.; Obiso, Vincenzo; Paynter, David; Thompson, David R.
The large uncertainty in mineral dust direct radiative effect (DRE) hinders projections of future climate change due to anthropogenic activity. Resolving modelled dust mineral-speciation allows for spatially and temporally varying refractive indices consistent with dust aerosol composition. Here, for the first time, we quantify the range in dust DRE at the top of the atmosphere (TOA) due to current uncertainties in the surface soil mineralogical content using a dust mineral-resolving climate model. We propagate observed uncertainties in soil mineral abundances from two soil mineralogy atlases along with the optical properties of each mineral into the DRE and compare the resultant range with other sources of uncertainty across six climate models. The shortwave DRE responses region-specifically to the dust burden depending on the mineral speciation and underlying shortwave surface albedo; positively when the regionally averaged annual surface albedo is larger than 0.28, and negatively otherwise. Among all minerals examined, the shortwave TOA DRE and single scattering albedo at the 0.44-0.63 µm band are most sensitive to the fractional contribution of iron oxides to the total dust composition. The global net (shortwave plus longwave) TOA DRE is estimated to be within -0.23 to +0.35 W m-2. Approximately 97% of this range relates to uncertainty in the soil abundance of iron oxides. Representing iron-oxide with solely hematite optical properties leads to an overestimation of shortwave DRE by +0.10 W m-2 at the TOA, as goethite is not as absorbing as hematite in the shortwave spectrum range. Our study highlights the importance of iron oxides to the shortwave DRE: they have a disproportionally large impact on climate considering their small atmospheric mineral mass fractional burden (~2%). An improved description of iron oxides, such as those planned in the Earth Surface Mineral Dust Source Investigation (EMIT), is thus essential for more accurate estimates of the dust DRE. This dataset supports this study.
This work was supported by the NASA EMIT project and the Earth Venture – Instrument program. We acknowledge high-performance computing resources provided by NCAR’s Computational and Information Systems Laboratory. LLL, NMM, and DSH was supported by the Atkinson Centre for a Sustainable Future. JFK acknowledges support from NSF grant 1552519. MK has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 789630. CPGP and MG acknowledge support by the European Research Council (grant no. 773051, FRAGMENT), the EU H2020 project FORCES (grant no. 821205), the AXA Research Fund, the Spanish Ministry of Science, Innovation and Universities (RYC-2015-18690 and NUTRIENT: CGL2017-88911-R), and PRACE and RES for awarding access to MareNostrum at the Barcelona Supercomputing Center to run MONARCH. RLM acknowledges support from the NASA Modeling, Analysis and Prediction Program (NNG14HH42I).
Dust-radiation interaction; iron oxides; soil mineralogy; dust modelling
Li, L., Mahowald, N. M., Miller, R. L., Pérez García-Pando, C., Klose, M., Hamilton, D. S., Gonçalves Ageitos, M., Ginoux, P., Balkanski, Y., Green, R. O., Kalashnikova, O., Kok, J. F., Obiso, V., Paynter, D., and Thompson, D. R.: Quantifying the range of the dust direct radiative effect due to source mineralogy uncertainty, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2020-547, in review, 2020.
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