Mineral Dust Aerosols: Ecological and radiative impacts

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Mineral dust aerosols affect climate directly through the scattering and absorbing of shortwave and thermal radiation and currently account for the largest uncertainty in the radiative forcing within current global climate models. Terrestrial and marine ecosystems in arid regions rely on the atmospheric deposition of mineral aerosols as a result of wind erosion to provide essential soluble nutrients. Currently, mineral dust emission schemes used within global climate models are based on theoretical models parameterized and corrected with highly idealized laboratory results. This simplification leads to simulated emissions that poorly represent actual transported size distributions and therefore mineral dust production and deposition rates. Although mass conservation is maintained in the models, biased rates of flux occur for minerals and nutrients from the source material, resulting in poor estimates of the biological impact of wind erosion. The proposed research program seeks to provide a new approach to the dynamic wind erosion process for measuring and quantifying mineral dust emissions. The program consists of two complementary methodological approaches to establish the role and impact of mineral dust size and chemical distributions throughout the transport process. First, it will evaluate the change in particle size distribution and associated mineralogy of particles as a result from the transport process through a series of laboratory wind tunnel investigations with natural and fabricated soils. These proposed investigations will seek to quantify the enrichment of nutrients in the transportation process to estimate the differences in the radiative and biological properties of mineral aerosols from their parent soils. Secondly, a novel methodology to measure dust emission fluxes is proposed using eddy covariance to provide more reliable estimates over traditional time-averaged methods. A series of comparative field studies in Namibia will utilize these different approaches over a range of surfaces to provide the first such set of this data. The chosen field sites are situated in regions that are directly impacted by the fertilizing component of mineral dust they receive. These results will be tested against current dust emission flux models to improve the performance of existing models and redefine standard procedures for measuring mineral dust emissions. This proposed research program will increase the ability for forecasting dust storms and their impacts on society and the natural environment. This new research will also improve the ability to predict the timing and severity of visibility and associated transport hazard systems within Canadian prairies and other arid zones.**