A Computationally Efficient Linear Semi-Lagrangian Scheme for the Advection of Microphysical Variables in Cloud-Resolving Models
A Computationally Efficient Linear Semi-Lagrangian Scheme for the Advection of Microphysical Variables in Cloud-Resolving Models
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DOI：
10.1175/mwr-d-19-0080.1
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发表时间：
2020-08
影响因子：
3.2
通讯作者：
E. Gavze;E. Ilotoviz;A. Khain
中科院分区：
文献类型：
--
作者：
E. Gavze;E. Ilotoviz;A. Khain
本文提出了一种云分辨模式中正定微物理量平流的有效半拉格朗日数值方案。该格式是一阶和二阶SL格式的线性组合。该计划进行了比较，两个高阶，单调，非线性欧拉计划，在两个二维测试。在第一个测试中，平流的正标量场与大梯度内进行复杂的理想化的转向流。在第二个测试中，使用2D希伯来大学云模型模拟冰雹风暴，描述不同微物理量的15个大小分布之间的相互作用（每个分布由43个质量箱描述）。该格式具有计算效率高、数值扩散小、质量守恒精度高等优点，并保持了多个平流变量之和以及平流标量变量之间的线性关系。虽然建议的SL计划是不完全正定的，负值和它们的数量，这可能只出现在非常强的梯度的情况下，是可以忽略不计的。该方案产生的结果类似于非线性欧拉平流方案，同时减少计算时间约10倍。
An efficient semi-Lagrangian (SL) numerical scheme for the advection of positive-definite microphysical variables in cloud-resolving models is proposed. The scheme is a linear combination of SL schemes of the first and second order. The proposed scheme is compared with two high-order, monotonic, nonlinear Eulerian schemes, in two 2D tests. In the first test, advection of a positive scalar field with large gradients is performed within complicated idealized steering flows. In the second test, a hail storm is simulated using the 2D Hebrew University Cloud Model, describing the interactions between 15 size distributions of different microphysical quantities (each distribution is described by 43 mass bins). The proposed scheme is computationally efficient, has a low numerical diffusion and a high level of mass conservation accuracy, and preserves the sum of multiple advected variables as well as the linear relationships between the advected scalar variables. Although the proposed SL scheme is not exactly positive definite, the negative values and their number, which may appear only in the case of very strong gradients, are negligible. The scheme produces results similar to those of nonlinear Eulerian advection schemes while reducing computation time by approximately a factor of 10.