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dc.contributor.authorOtto, Sebastian
dc.contributor.authorBierwirth, Eike
dc.contributor.authorWeinzierl, Bernadett
dc.contributor.authorKandler, Konrad
dc.contributor.authorEsselborn, Michael
dc.contributor.authorTesche, Matthias
dc.contributor.authorSchladitz, Alexander
dc.contributor.authorWendisch, Manfred
dc.contributor.authorTrautmann, Thomas
dc.identifier.citationOtto , S , Bierwirth , E , Weinzierl , B , Kandler , K , Esselborn , M , Tesche , M , Schladitz , A , Wendisch , M & Trautmann , T 2009 , ' Solar radiative effects of a Saharan dust plume observed during SAMUM assuming spheroidal model particles ' , Tellus Series B-Chemical and Physical Meteorology , vol. 61 , no. 1 , pp. 270-296 .
dc.identifier.otherPURE: 8757693
dc.identifier.otherPURE UUID: 380ce50e-04c0-43ec-be7d-fe69841b84b7
dc.identifier.otherScopus: 58849108570
dc.description.abstractThe solar optical properties of Saharan mineral dust observed during the Saharan Mineral Dust Experiment (SAMUM) were explored based on measured size-number distributions and chemical composition. The size-resolved complex refractive index of the dust was derived with real parts of 1.51-1.55 and imaginary parts of 0.0008-0.006 at 550 nm wavelength. At this spectral range a single scattering albedo ωo and an asymmetry parameter g of about 0.8 were derived. These values were largely determined by the presence of coarse particles. Backscatter coefficients and lidar ratios calculated with Mie theory (spherical particles) were not found to be in agreement with independently measured lidar data. Obviously the measured Saharan mineral dust particles were of non-spherical shape. With the help of these lidar and sun photometer measurements the particle shape as well as the spherical equivalence were estimated. It turned out that volume equivalent oblate spheroids with an effective axis ratio of 1:1.6 matched these data best. This aspect ratio was also confirmed by independent single particle analyses using a scanning electron microscope. In order to perform the non-spherical computations, a database of single particle optical properties was assembled for oblate and prolate spheroidal particles. These data were also the basis for simulating the non-sphericity effects on the dust optical properties: ωo is influenced by up to a magnitude of only 1% and g is diminished by up to 4% assuming volume equivalent oblate spheroids with an axis ratio of 1:1.6 instead of spheres. Changes in the extinction optical depth are within 3.5%. Non-spherical particles affect the downwelling radiative transfer close to the bottom of the atmosphere, however, they significantly enhance the backscattering towards the top of the atmosphere: Compared to Mie theory the particle non-sphericity leads to forced cooling of the Earth-atmosphere system in the solar spectral range for both dust over ocean and desert.en
dc.relation.ispartofTellus Series B-Chemical and Physical Meteorology
dc.subjectAtmospheric Science
dc.titleSolar radiative effects of a Saharan dust plume observed during SAMUM assuming spheroidal model particlesen
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.description.statusPeer reviewed
rioxxterms.typeJournal Article/Review

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