Preferential deposition of snow and dust over hills: governing processes and relevant scales

Preferential deposition of snow and dust over complex terrain is responsible for a wide range of environmental processes, and accounts for a significant source of uncertainty in surface mass balances of cold and arid regions. Despite the growing body of literature on the subject, previous studies reported contradictory results on the location and magnitude of deposition maxima and minima. This study aims at unraveling the governing processes of preferential deposition in neutrally stable atmosphere and to reconcile seemingly inconsistent results of previous works. For this purpose, a comprehensive modeling approach is developed, based on large eddy simulations of the turbulent airflow, Lagrangian stochastic model of particle trajectories, and immersed-boundary method to represent the underlying topography. The model performance is tested against wind tunnel measurements of dust deposition around isolated and sequential hills. A scale analysis is then performed to investigate the dependence of snowfall deposition on the particle Froude and Stokes numbers, which fully account for the governing processes of inertia, flow advection, and gravity. Additional simulations are performed, to test whether the often used assumption of inertialess particles yields accurate deposition patterns. We finally show that our scale analysis provides qualitatively similar results for hills with different aspect ratios. This dataset contains the results of the LES-LSM model. Each Matlab file contains a 2D array of deposition values (in kg/m2) in each surface node (ix, iy) of the Cartesian grid. The file names are consistent with the simulation numbers listed in the original paper. For additional information, please refer to "Preferential deposition of snow and dust over hills: governing processes and relevant scales" by F. Comola, M. G. Giometto, S. T. Salesky, M. B. Parlange, and M. Lehning, Journal of Geophysical Research: Atmospheres, 2019.复杂地形上风雪与沙尘的优先沉积（Preferential Deposition）主导了一系列环境过程，同时构成了寒冷干旱区地表质量平衡不确定性的重要来源。尽管该领域的研究成果日益丰富，但既往研究针对沉积极值的位置与强度得出了相互矛盾的结论。本研究旨在阐明中性稳定大气条件下优先沉积的控制机制，并调和以往研究中看似不一致的结果。为此，本研究基于湍流气流的大涡模拟（Large Eddy Simulations, LES）、粒子轨迹的拉格朗日随机模型（Lagrangian Stochastic Model）以及用于表征下垫面地形的浸入边界法（Immersed-Boundary Method），开发了一套综合建模方法。针对孤立山丘与连续山丘周边的沙尘沉积风洞测量数据，对该模型的性能进行了验证。随后开展尺度分析，以探究降雪沉积对粒子弗劳德数（Froude Number）与斯托克斯数（Stokes Number）的依赖关系，这两个参数完整涵盖了惯性、流动平流与重力等核心控制过程。额外开展模拟实验，以检验常用的无惯性粒子假设能否生成准确的沉积格局。本研究最终证明，针对不同高宽比的山丘，本研究的尺度分析可得到定性一致的结果。 本数据集包含LES-LSM模型的运算结果。每个Matlab文件均存储笛卡尔网格各表面节点(ix, iy)处的沉积通量值（单位：kg/m²）构成的二维数组。文件名与原论文中列出的模拟编号一一对应。如需获取更多信息，请参阅F. Comola、M. G. Giometto、S. T. Salesky、M. B. Parlange及M. Lehning于2019年发表在《Journal of Geophysical Research: Atmospheres》的论文《山丘上风雪与沙尘的优先沉积：控制机制与相关尺度（Preferential deposition of snow and dust over hills: governing processes and relevant scales）》。