The Numerical Modelling of the Sedimentation of Polar Stratospheric Cloud Particles
The Numerical Modelling of the Sedimentation of Polar Stratospheric Cloud Particles
复制标题
极地平流层云粒子沉积的数值模拟
DOI：
--
复制
发表时间：
1992
期刊：
影响因子：
--
通讯作者：
T. Peter
中科院分区：
文献类型：
--
作者：
R. Müller;T. Peter
极夜平流层的反硝化对于控制北极和南极地区平流层臭氧消耗量至关重要。它是通过极地平流层云 (PSC) 颗粒的形成和沉积来完成的。后一个过程虽然概念上很简单，但不容易纳入 PSC 数值模型中。我们提出了计算实验的结果，展示了各种数值方法的优点和缺陷。假设的速度分布与真实粒子速度分布相似，但足够简单，可以对平流方程进行解析解。所提出的方案是逆风偏置有限体积方案，具有许多所需的性质，特别是质量守恒和正定性。数值扩散提出了一个主要问题，特别是因为观察到 PSC 表现出明显的分层，这需要对粒子数密度的陡峭梯度进行建模。另一方面，如果允许多个网格盒上的半拉格朗日平流，则可以引入人工结构。描述了避免这些困难的程序，特别是多项式拟合，并研究了该方案的计算效率。我们得出的结论是，多项式拟合是处理 PSC I 型颗粒的合适方法，而我们推荐一种新颖的半拉格朗日方法，该方法的设计可以避免针对 PSC II 型颗粒的人工结构。
The denitrification of the polar night stratosphere is crucially controlling the amount of stratospheric ozone depletion over both the Arctic and Antarctic. It is accomplished through the formation and sedimentation of polar stratospheric cloud (PSC) particles. The latter process, though conceptionally simple, is not easily incorporated into numerical PSC models. We present results of computational experiments demonstrating advantages and pitfalls of various numerical methods. The velocity profiles which are assumed are similar to real particle velocity profiles, but simple enough to allow an analytic solution of the advection equation. The proposed schemes are upwind biased finite volume schemes, possessing many desired properties, in particular mass conservation and positive definiteness. Numerical diffusion presents a major problem, particularly since PSCs are observed to exhibit pronounced layering which requires the modelling of steep gradients in the particle number density. On the other hand, artificial structures can be introduced if semi-Lagrangian advection over several grid boxes is allowed. Procedures obviating these difficulties are described, in particular polynomial fitting, and the computational efficiency of the schemes is investigated. We conclude that polynomial fitting is a suitable method for treating PSC Type-I particles, whereas we recommend a novel semi-Lagrangian method, designed so that artificial structures can be avoided, for PSC Type-II particles.