Inferring iron oxides species content in atmospheric mineral dust from DSCOVR EPIC observations

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dc.contributor.authorGo, Sujung
dc.contributor.authorLyapustin, Alexei
dc.contributor.authorSchuster, Gregory L.
dc.contributor.authorChoi, Myungje
dc.contributor.authorGinoux, Paul
dc.contributor.authorChin, Mian
dc.contributor.authorKalashnikova, Olga
dc.contributor.authorDubovik, Oleg
dc.contributor.authorKim, Jhoon
dc.contributor.authorSilva, Arlindo da
dc.contributor.authorHolben, Brent
dc.contributor.authorReid, Jeffrey S.
dc.date.accessioned2021-09-16T14:40:26Z
dc.date.available2021-09-16T14:40:26Z
dc.date.issued2021-08-27
dc.description.abstractThe iron-oxide content of dust in the atmosphere and most notably its apportionment between hematite (α-Fe2O3) and goethite (α-FeOOH) are key determinants in quantifying dust's light absorption, its top of atmosphere UV radiances used for dust monitoring, and ultimately shortwave dust direct radiative effects (DRE). Hematite and goethite column mass concentrations and iron-oxide mass fractions of total dust mass concentration were retrieved from the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) measurements in the ultraviolet–visible (UV–Vis) channels. The retrievals were performed for dust-identified aerosol plumes using aerosol optical depth (AOD) and spectral imaginary refractive index provided by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm over six continental regions (North America, North Africa, West Asia, Central Asia, East Asia, and Australia). The dust particles are represented as an internal mixture of non-absorbing host and absorbing hematite and goethite. We use the Maxwell–Garnett effective medium approximation with carefully selected complex refractive indices of hematite and goethite that produce mass fractions of iron oxides species consistent with in situ values found in the literature to derive the hematite and goethite volumetric/mass concentrations from MAIAC EPIC products. We compared the retrieved hematite and goethite concentrations with in situ dust aerosol mineralogical content measurements, as well as with published data. Our data display variations within the published range of hematite, goethite, and iron-oxide mass fractions for pure mineral dust cases. A specific analysis is presented for 15 sites over the main dust source regions. Sites in the central Sahara, Sahel, and Middle East exhibit a greater temporal variability of iron oxides relative to other sites. Niger site (13.52° N, 2.63° E) is dominated by goethite over Harmattan season with median of ~2 weight percentage (wt.%) of iron-oxide. Saudi Arabia site (27.49° N, 41.98° E) over Middle East also exhibited surge of goethite content with the beginning of Shamal season. The Sahel dust is richer in iron-oxide than Saharan and northern China dust except in Summer. The Bodélé Depression area shows a distinctively lower iron-oxide concentration (~1 wt. %) throughout the year. Finally, we show that EPIC data allow to constrain the hematite refractive index. Specifically, we select 5 out of 13 different number of hematite refractive indices widely variable in published laboratory studies by constraining the iron-oxide mass ratio to the known measured values. Provided climatology of hematite and goethite mass fractions across main dust regions of the Earth will be useful for dust shortwave DRE studies and climate modeling.en_US
dc.description.sponsorshipThe work of A. Lyapustin, S. Go, and M. Choi was funded by the NASA DSCOVR program (manager Dr. R. Eckman) and in part by the NASA PACE program (19-PACESAT19-0039). We are grateful to the AERONET team for providing validation data and to the NASA Center for Climate Simulations providing resources for the EPIC data processing. Co-author J. S Reid was supported by the Office of Naval Research Code 322.en_US
dc.description.urihttps://acp.copernicus.org/articles/22/1395/2022/en_US
dc.format.extent29 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2cqmw-gon4
dc.identifier.citationGo, S., Lyapustin, A., Schuster, G. L., Choi, M., Ginoux, P., Chin, M., Kalashnikova, O., Dubovik, O., Kim, J., da Silva, A., Holben, B., and Reid, J. S.: Inferring iron-oxide species content in atmospheric mineral dust from DSCOVR EPIC observations, Atmos. Chem. Phys., 22, 1395–1423, https://doi.org/10.5194/acp-22-1395-2022, 2022.en_US
dc.identifier.urihttps://doi.org/10.5194/acp-22-1395-2022
dc.identifier.urihttp://hdl.handle.net/11603/22996
dc.language.isoen_USen_US
dc.publisherEGUen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Joint Center for Earth Systems Technology
dc.relation.ispartofUMBC Faculty Collection
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.en_US
dc.rightsPublic Domain Mark 1.0*
dc.rights.urihttps://creativecommons.org/publicdomain/mark/1.0/*
dc.titleInferring iron oxides species content in atmospheric mineral dust from DSCOVR EPIC observationsen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-0223-309Xen_US
dcterms.creatorhttps://orcid.org/0000-0002-2488-2840en_US

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