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Author: Schepanski, K. × Subject: atmospheric deposition ×

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Now showing 1 - 2 of 2
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    Mass deposition fluxes of Saharan mineral dust to the tropical northeast Atlantic Ocean: An intercomparison of methods
    (München : European Geopyhsical Union, 2014) Niedermeier, N.; Held, A.; Müller, T.; Heinold, B.; Schepanski, K.; Tegen, I.; Kandler, K.; Ebert, M.; Weinbruch, S.; Read, K.; Lee, J.; Fomba, K.W.; Müller, K.; Herrmann, H.; Wiedensohler, A.
    Mass deposition fluxes of mineral dust to the tropical northeast Atlantic Ocean were determined within this study. In the framework of SOPRAN (Surface Ocean Processes in the Anthropocene), the interaction between the atmosphere and the ocean in terms of material exchange were investigated at the Cape Verde atmospheric observatory (CVAO) on the island Sao Vicente for January 2009. Five different methods were applied to estimate the deposition flux, using different meteorological and physical measurements, remote sensing, and regional dust transport simulations. The set of observations comprises micrometeorological measurements with an ultra-sonic anemometer and profile measurements using 2-D anemometers at two different heights, and microphysical measurements of the size-resolved mass concentrations of mineral dust. In addition, the total mass concentration of mineral dust was derived from absorption photometer observations and passive sampling. The regional dust model COSMO-MUSCAT was used for simulations of dust emission and transport, including dry and wet deposition processes. This model was used as it describes the AOD's and mass concentrations realistic compared to the measurements and because it was run for the time period of the measurements. The four observation-based methods yield a monthly average deposition flux of mineral dust of 12–29 ng m−2 s−1. The simulation results come close to the upper range of the measurements with an average value of 47 ng m−2 s−1. It is shown that the mass deposition flux of mineral dust obtained by the combination of micrometeorological (ultra-sonic anemometer) and microphysical measurements (particle mass size distribution of mineral dust) is difficult to compare to modeled mass deposition fluxes when the mineral dust is inhomogeneously distributed over the investigated area.
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    Saharan dust transport and deposition towards the tropicalnorthern Atlantic
    (Göttingen : Copernicus, 2009) Schepanski, K.; Tegen, I.; MacKe, A.
    We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bod́eĺe Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bod́eĺe dust transported towards the Cape Verde Islands is evident in winter when the Bod́eĺe source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.