Abstract
Abstract. Cellular-automata-based modelling for simulating snow bedforms and snow deposition is introduced in this study. The well-known ReSCAL model, previously used for sand bedforms, is adapted for this purpose by implementing a simple sintering mechanism. The effect of sintering is first explored for solitary barchan dunes of different sizes and flow conditions. Three types of behaviour are observed: small barchans continue their motion without any perceptible difference while large barchans sinter immediately. Barchans of intermediate size split, leaving behind a sintered core and a smaller barchan is formed. It is found that sintering introduces an upper limit to the size of bedforms that can remain mobile. The concept of “maximum streamwise length” (MSL) is introduced and MSL is identified for different wind speeds using the solitary dune scenario. Simulations of the full evolution from an initially flat snow layer to a complex dune field are performed next. It is found that the largest bedforms lie below the MSL threshold. Additionally, it is found that shallow snow layers are most susceptible to mechanical destabilization by the wind.
Highlights
Under the action of wind blowing over a layer of freshly deposited snow, snow reorganizes due to aeolian transport mechanisms into a number of shapes and bedforms; an initially flat surface may evolve into an undulated surface with significant height variations due to bedforms of various length scales
In the first section in this study, we performed a series of numerical experiments to investigate the morphodynamics of a solitary barchan dune
Even without accounting for the effect of sintering, some new insights were gained since the scale of dunes simulated (O 10 m), while relevant for snow bedforms, was an order of magnitude smaller than barchans found in sand (O 100 m), which are more well-studied
Summary
Under the action of wind blowing over a layer of freshly deposited snow, snow reorganizes due to aeolian transport mechanisms into a number of shapes and bedforms; an initially flat surface may evolve into an undulated surface with significant height variations due to bedforms of various length scales. Computational modelling has played a central role in improving the understanding of aeolian transport processes both at the grain scale and for developing parametrizations for mechanisms at different scales in the context of both sand and snow transport. At the smallest relevant scale of grain-scale interactions, discrete element modelling (DEM) has allowed for linking material properties to transport mechanisms following the pioneering work of Anderson and Haff (1988) Narteau et al (2009) introduced a new CA-based model named ReSCAL that overcame a major shortcoming of the earlier CA-based models by coupling the CA model of the granular material to a CA model for the air This allowed, for the first time, the simulation of the complete feedback between the evolving surface, the resultant perturbations in the flow and its impact on aeolian transport.
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