Clouds in observations are fractals: they show self-similarity across scales ranging from 1 to 1,000 km. This includes individual storms and large-scale cloud structures typical of organized convection. It is not known whether global storm-resolving models reproduce the observed fractal scaling laws for clouds and organized convection. We compute the fractal dimension of clouds using Himawari satellite data and compare this to global storm-resolving model simulations completed as part of the DYAMOND intercomparison project. We find cloud fields in these simulations are indeed fractal, and reproduce the observed fractal dimension to within 10%. We find the fractal dimension is sensitive to the choice of boundary layer parametrization scheme used in each model simulation, and not to the convection parametrization as might have been expected.

中文翻译：

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全球风暴解决模型中云的分形性质

观测中的云是分形的：它们在 1 到 1,000 公里的尺度上表现出自相似性。这包括个别风暴和典型的有组织的对流的大规模云结构。目前尚不清楚全球风暴解决模型是否再现了观察到的云和有组织对流的分形缩放规律。我们使用 Himawari 卫星数据计算云的分形维数，并将其与作为 DYAMOND 比对项目的一部分完成的全球风暴解决模型模拟进行比较。我们发现这些模拟中的云场确实是分形的，并且将观察到的分形维数重现到 10% 以内。我们发现分形维数对每个模型模拟中使用的边界层参数化方案的选择很敏感，而不是像预期的那样对对流参数化。