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.复杂地形上降雪与粉尘的优先沉积主导了诸多环境过程，同时也是寒冷干旱区地表质量平衡不确定性的重要来源。尽管相关研究文献日益丰富，但既往研究针对沉积极值的位置与强度所得结论却存在矛盾。本研究旨在阐明中性稳定大气中优先沉积的控制机制，并调和既往研究中看似不一致的结果。为此，本文基于湍流气流的大涡模拟（Large Eddy Simulations, LES）、粒子轨迹拉格朗日随机模型（Lagrangian Stochastic Model）以及用于表征下伏地形的浸入边界法（Immersed-Boundary Method），构建了一套完整的建模框架。通过孤立山丘与连续山丘周围粉尘沉积的风洞测量数据，对模型性能进行了验证。随后开展了尺度分析，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，这两个参数充分涵盖了惯性、流动平流与重力等控制过程。额外开展的模拟实验用于检验常用的无惯性粒子假设能否得到准确的沉积分布模式。最后，本研究证明，所提出的尺度分析对不同长径比的山丘均可得到定性一致的结果。 本数据集包含LES-LSM模型的模拟结果。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（单位：kg/m²）的二维数组。文件名与原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发表于《Journal of Geophysical Research: Atmospheres》2019年的论文《Preferential deposition of snow and dust over hills: governing processes and relevant scales》。