Alejandra Vicaría Aguilar
Published: 2020
Total Pages:
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Radiative forcing on the atmosphere due to mineral dust aerosols plays a key role in climate change. This results from dust optical properties, more specifically the Single Scattering Albedo (SSA), which is a key aerosol optical parameter and determines sign and magnitude of radiative forcing due to aerosols. In order to get a better understanding of how mineral dust aerosols have an impact on climate, it is of great importance the study of the variability of the mineralogical composition of airborne dust. Here, we revise two data sets that provide mineralogical information for several soil units of the clay and the silt fraction of the soil based on the relative abundance of selected minerals. Furthermore, this paper is focused on the study of the variability of the relative abundance of iron oxide minerals and mean iron content of soils, which are key to determine the SSA of mineral dust in the short-wave spectrum. A regional analysis is conducted in the Sahara desert, located in northern Africa, to study the variability in the relative abundance of hematite and goethite according to each data set. These analyses are conducted by statistical analyses and developing adequate MATLAB codes in order to obtain the desired results. Results show a high variability and large uncertainties on the definition of iron oxide minerals in the erodible fraction of the soil, presenting high coefficients of variance for both data sets. This uncertainty on the resulting values is due to lack of mineralogical data and hypothesis that have been assumed in order to provide more geographical coverage. Mineralogical maps in a 0.5' x 0.5' grid, have been constructed from data extracted from the databases in order to display geographical distribution of the mineralogical composition at a global or regional scale. Finally, the SSA of mineral dust, at two wavelengths 405 nm and 870 nm, basing the calculations on the linear relationship established in Moosmüller et al. (2012), that relates the iron content to the SSA. This optical parameter calculated for 12 textural soil classes and for the region of the Sahara desert. Results present a high SSA in both case analyses, but when calculating the SSA for the Sahara region, the SSA is relatively higher to those presented in the theoretical calculations for the soil textural classes. Nevertheless, as we obtain a high values, as expected, it is confirmed that iron content in mineral dust affects significantly the values of the Single Scattering Albedo.