Convection Cells in the Planetary Boundary Layer: Origin and Reduced Modeling

在自由对流条件下，行星边界层中的流动是以长期、大规模的蜂窝运动来组织的。我们想要调查这些上层建筑。特别是，我们想要确定边界条件对它们的形成和演化有多重要，以及我们如何在简单的大气模型中表示它们。我们将使用直接数值模拟的数据。从Rayleigh-Bénard对流开始，我们将逐步修改边界条件，以设计和研究对流边界层，这是再现大气流动关键方面的理想构型。其目的是了解超结构对边界条件和瑞利数的依赖关系。为了探测超结构并分析它们与小尺度湍流的相互作用，我们将使用粗粒化和拉格朗日技术。作为这项工作的结果，我们将全面了解这些技术在表示行星边界层中的超结构方面的效率。此外，该项目将把瑞利-伯纳德对流和大气对流合并在一个单一的分析中，从而评估我们可以在这两个领域之间传递知识的程度。

Under free-convection conditions, the flow in the planetary boundary layer is organized in long-lived, large-scale cellular motions. We want to investigate these superstructures. In particular, we want to ascertain how important the boundary conditions are for their formation and evolution, and how we can represent them in simple atmospheric models. We will employ data from direct numerical simulations. Starting from Rayleigh-Bénard convection, we will incrementally modify the boundary conditions to design and study convective boundary layers, which are idealized configurations that reproduce key aspects of the atmospheric flow. The aim is to understand the dependence of superstructures on the boundary conditions, and on the Rayleigh number. For the detection of the superstructures and the analysis of their interaction with the small-scale turbulence, we will use coarse-graining and Lagrangian techniques. As an outcome of this work, we will comprehensively learn how efficient these techniques are to represent superstructures in the planetary boundary layer. Besides, this project will bring together Rayleigh-Bénard convection and atmospheric convection in one single analysis, assessing thereby to what extent we can transfer knowledge between the two fields.