Model simulations of dust sources and transport in the global atmosphere. Effects of soil erodibility and wind speed variability

Global atmospheric dust is simulated using DEAD (Dust Entrainment and Deposition model) in combination with the global scale Oslo CTM2 using meteorological data for 1996. Dust sources are calculated both using mean wind speeds with model resolution (T63) and sub-grid wind speeds. Different datasets are used to describe soil erodibility. We explain how the different assumptions on dust production affect atmospheric dust burden and deposition. Some aspects of the annual dust cycle, such as the east Asian dust emissions are largely dependent on the data used to determine soil erodibility. Other aspects, such as the timing of the maximum in the African plume at Northern hemisphere summer is well modeled with all datasets applied here. We show that the daily variation in optical depth at Cape Verde at the west coast of Africa is well simulated when we assume that erodibility is correlated with surface reflectivity from MODIS satellite data. Using a sub-grid probability density function of wind speed to drive the dust sources facilitates dust emissions in areas with low wind speeds. Dust concentrations in remote areas are sensitive to the parameterization of wet deposition. Our results point out to need for a detailed soil erodibility dataset for global dust modeling, and they suggest that surface reflectivity is potentially valuable for producing or evaluating such datasets.