Abstract

Helicity is inherent in many circulating motions and structures in the atmospheric boundary layer (ABL), where it is continuously reproduced due to the combined action of the Earth’s rotation and friction, which also is closely related to the phenomena of the inverse cascade and large-scale restructuring of flows. The helicity factor should be correctly considered during the construction of atmosphere models, and, accordingly, the knowledge of the helicity distribution in the ABL and its relation to dynamic atmospheric processes is required. In this study, the helicity of the circulation structures of various spatial and temporal scales in the ABL is determined from an analysis of field measurement data. A qualitative and quantitative comparison with the observed values is carried out on the basis of results of numerical simulations using the quasi-two-dimensional model and a WRF-ARW mesoscale atmospheric nonhydrostatic model, in particular, WRF-LES. A good agreement with the observed spatial distributions of circulating motions is obtained. A link between the turbulent characteristics and helicity of the structures under study is shown. The helicity estimates for circulation structures of various scales in the ABL and in the free atmosphere are compared.

中文翻译：

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大气边界层的螺旋度和湍流

摘要

螺旋是大气边界层（ABL）中许多循环运动和结构所固有的，由于地球自转和摩擦的联合作用，螺旋在其中不断复制，这也与反向叶栅现象和大直径现象密切相关。流量规模重组。在建立大气模型时应正确考虑螺旋度因子，因此，需要了解ABL中的螺旋度分布及其与动态大气过程的关系。在这项研究中，通过对现场测量数据的分析来确定ABL中各种时空尺度的环流结构的螺旋度。基于数值模拟的结果，使用准二维模型和WRF-ARW中尺度大气非静水模型，特别是WRF-LES，与观测值进行了定性和定量比较。获得与所观察到的循环运动的空间分布的良好一致性。显示了所研究结构的湍流特性和螺旋度之间的联系。比较了ABL和自由大气中各种尺度的循环结构的螺旋度估计值。