Abstract
Abstract. We develop a parameterization scheme of convective dust emission for regional and global atmospheric models. Convective dust emission occurs in the absence of saltation as large eddies intermittently produce strong shear stresses on the surface and entrain dust particles into the air. This dust emission mechanism has not been included in the traditional dust models. The scheme presented in this study is a new approach which takes account of the stochastic nature of convective dust emission. It consists of the statistical representations of soil particle size, inter-particle cohesion, and instantaneous surface shear stress. A method of determining the probability density function of the latter quantity is proposed. Dust emission is then estimated from the overlap of the probability density functions of the aerodynamic lifting and inter-particle cohesive forces. The new scheme is implemented into the WRF/Chem model and applied to dust modeling in the Taklimakan Desert. A comparison with lidar data shows that the model can reproduce the main features of the dust patterns and their diurnal variations. For the case studied, convective dust emission is typically several μg m−2 s−1 and at times up to 50 μg m−2 s−1.
Highlights
The existing dust emission schemes used in regional and global atmospheric models are mainly concerned with the parameterization of dust emission caused by saltation bombardment (e.g. Marticorena and Bergametti, 1995) and aggregates disintegration (e.g. Shao, 2004)
Up to about 1500 kg s−1 of dust are emitted at noon time each day by convective turbulence
Advection is relatively small during the study period due to the weak winds. δD reaches up to 1000 kg s−1 at noon time
Summary
The existing dust emission schemes used in regional and global atmospheric models are mainly concerned with the parameterization of dust emission caused by saltation bombardment (e.g. Marticorena and Bergametti, 1995) and aggregates disintegration (e.g. Shao, 2004). As pointed out in previous studies (Marticorena et al, 1997; Shao et al, 1993), the intensity of dust emission due to direct aerodynamic lifting is much weaker than that due to saltation bombardment and aggregates disintegration, and can be neglected in modeling strong dust events (e.g. dust storms). Ito et al (2010) carried out a large-eddy simulation (LES) to estimate convective dust emission They considered a particle size range from 1 to 10 μm and computed the dust fluxes according to Loosmore and Hunt (2000). The second aim of the study is to develop the capacity of assessing the contribution of convective dust emission to regional and global dust budgets To this end, a technique is proposed to implement the new scheme in the framework of the WRF/Chem model. The model results are compared with the lidar data collected at Aksu
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