Collection/aggregation algorithms in Lagrangian cloud microphysical models: Rigorous evaluation in box model simulations
Collection/aggregation algorithms in Lagrangian cloud microphysical models: Rigorous evaluation in box model simulations
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DOI：
10.5194/gmd-10-1521-2017
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发表时间：
2016-11
影响因子：
5.1
通讯作者：
S. Unterstrasser;F. Hoffmann;Marion Lerch
中科院分区：
文献类型：
--
作者：
S. Unterstrasser;F. Hoffmann;Marion Lerch
抽象的。最近，已经开发了几种拉格朗日微物理模型，它们使用大量（计算）粒子来表示云。特别是，导致云滴合并或冰晶聚集的碰撞过程在各种模型中的实现方式不同。审查和扩展了三个现有的实现，并通过与完善的分析和 bin 模型解决方案进行比较来评估它们的性能。在严格评估的第一步中，我们对 Golovin、Long 和 Hall 三个著名的内核进行了盒模型模拟，其中收集/聚合是唯一考虑的过程。除了时间步长和所使用的模拟粒子 (SIP) 数量等数值参数之外，如何根据规定的分析定义的尺寸分布创建初始 SIP 系综的细节对于算法的性能至关重要。正如之前的研究中所做的那样，使用恒定权重技术极大地低估了算法的质量。使用更好的初始化技术可以大大减少获得实际结果所需的 SIP 数量。根据盒模型结果，得出在高维模型设置中实施收集/聚合的建议。合适的算法同样适用于处理卷云中的暖雨过程和聚集。
Abstract. Recently, several Lagrangian microphysical models have been developed which use a large number of (computational) particles to represent a cloud. In particular, the collision process leading to coalescence of cloud droplets or aggregation of ice crystals is implemented differently in various models. Three existing implementations are reviewed and extended, and their performance is evaluated by a comparison with well-established analytical and bin model solutions. In this first step of rigorous evaluation, box model simulations, with collection/aggregation being the only process considered, have been performed for the three well-known kernels of Golovin, Long and Hall. Besides numerical parameters, like the time step and the number of simulation particles (SIPs) used, the details of how the initial SIP ensemble is created from a prescribed analytically defined size distribution is crucial for the performance of the algorithms. Using a constant weight technique, as done in previous studies, greatly underestimates the quality of the algorithms. Using better initialisation techniques considerably reduces the number of required SIPs to obtain realistic results. From the box model results, recommendations for the collection/aggregation implementation in higher dimensional model setups are derived. Suitable algorithms are equally relevant to treating the warm rain process and aggregation in cirrus.