Wind Erosion in Western Queensland Australia

Chapter 3 – Modelling Land Erodibility Review3.4.2 Dust Entrainment and Deposition Model (DEAD)The Dust Entrainment and Deposition Model (DEAD) is a global dust emission and transportmodel (Zender et al., 2003a). The dust entrainment and mobilisation scheme used in DEADis similar to that of Marticorena and Bergametti (1995). The model emission scheme isparticle size dependent, with u *t being computed as a function of soil particle sizedistributions. Modifications are made to u *t by accounting for soil moisture effects using thescheme of Fécan et al. (1999), and surface roughness effects using the drag partitioningscheme of Raupach et al. (1993). The model considers the Owen effect, a positive feedbackof saltation on the surface roughness length and friction velocity, using the model of Gilletteet al. (1998).Dust source area soil erodibilities in DEAD are defined by soil particle size distributions froma global soil texture dataset (Zender et al., 2003a). Land surface and geographic constraintsare applied to the dust source areas in addition to the roughness and moistureparameterisations in the emission scheme. The fraction of bare soil surface is described by aparameter which is a function of total vegetation, snow, lake and wetlands cover. Vegetationcover is derived from satellite imagery of Leaf Area Index (LAI) at a 1 x 1 km spatialresolution. These factors are considered constant during simulations. A further adjustment ismade for dust source area erodibility S. This adjustment has a basis in global dust source areacharacterisations reported by Ginoux et al. (2001), identified using Total Ozone MappingSpectrometer (TOMS) aerosol optical thickness image data. Zender et al. (2003a) defined Sas the upstream area from which sediment transported in surface runoff may haveaccumulated. The S parameter was included to account for the relationship between globaldust source area location and sediment recharge in drainage depressions. Zender et al.(2003b) reported on the effects of variants on the S parameter for uniform, topographic,geomorphic and hydrological source erodibility factors on global dust load predictions.Results demonstrated that simulations of global dust emissions are highly sensitive to dustsource area characterisations.Grini et al. (2005) examined dust sources and transport with DEAD using four soil erodibilityfactors. The soil erodibility factors were defined to capture characteristics of global dustsource areas and included the topographic and geomorphic factors used by Ginoux (2001)and Zender et al. (2003b), for example:89