An Intercomparison Among Four Models Of Blowing Snow

Four one-dimensional, time-dependent blowing snow models areintercompared. These include three spectral models, PIEKTUK-T,WINDBLAST, SNOWSTORM, and the bulk version of PIEKTUK-T,PIEKTUK-B. Although the four models are based on common physicalconcepts, they have been developed by different research groups. Thestructure of the models, numerical methods, meteorological field treatmentand the parameterization schemes may be different. Under an agreed standardcondition, the four models generally give similar results for the thermodynamic effects of blowing snow sublimation on the atmospheric boundary layer, including an increase of relative humidity and a decrease of the ambient temperature due to blowing snow sublimation. Relative humidity predicted by SNOWSTORM is lower than the predictions of the other models, which leads to a larger sublimation rate in SNOWSTORM. All four models demonstrate that sublimation rates in a column of blowing snow have a single maximum in time, illustrating self-limitation of the sublimation process of blowing snow. However, estimation of the eddy diffusioncoefficient for momentum (K_m), and thereby the diffusion coefficients for moisture (K_w) and for heat (K_h), has a significant influence on the process. Sensitivitytests with PIEKTUK-T show that the sublimation rate can be approximately constant with time after an initial phase, if K_m is a linear function with height. In order to match the model results with blowing snow observations, some parameters in the standard run, such as settling velocity of blowing snow particles in these models, may need to be changed to more practical values.