Separation frequency of large-scale anisotropic eddies and small-scale isotropic eddies in the near-neutral and unstable atmospheric surface layer

IF 1.8 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Journal of Atmospheric and Solar-Terrestrial Physics Pub Date : 2025-02-01 DOI:10.1016/j.jastp.2025.106429

Guowen Han, Bowen Zhang, Lixia Wang, Hongshuo Yan, Guowei Xin, Xiaobin Zhang

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引用次数: 0

Abstract

High-frequency fluctuations of streamwise, spanwise, and vertical velocity components were measured in the logarithmic region of the atmospheric surface layer (ASL) to analyze the separation frequency of large-scale anisotropic eddies and small-scale isotropic eddies in high Reynolds number wall turbulence. The experimental results indicate that the separation frequency decreases exponentially with height and increases linearly with friction velocity in the near-neutral ASL. Furthermore, our study investigated the impact of atmospheric thermal stability on the separation frequency and revealed a decrease in the separation frequency with increasing thermal buoyancy in the ASL. By analyzing the mean wind shear in the near-neutral and unstable ASL at different heights, our study suggested that mean wind shear destroys large-scale turbulent eddies, transforming them into small-scale turbulent eddies. This phenomenon may lead to variations in the separation frequency with height, friction velocity, and atmospheric thermal stability. Our findings may shed new light on the understanding of atmospheric turbulence dynamics and its implications for the local-isotropy hypothesis in the ASL.

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来源期刊

Journal of Atmospheric and Solar-Terrestrial Physics 地学-地球化学与地球物理

CiteScore

4.10

自引率

5.30%

发文量

审稿时长

6 months

期刊介绍： The Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) is an international journal concerned with the inter-disciplinary science of the Earth''s atmospheric and space environment, especially the highly varied and highly variable physical phenomena that occur in this natural laboratory and the processes that couple them. The journal covers the physical processes operating in the troposphere, stratosphere, mesosphere, thermosphere, ionosphere, magnetosphere, the Sun, interplanetary medium, and heliosphere. Phenomena occurring in other "spheres", solar influences on climate, and supporting laboratory measurements are also considered. The journal deals especially with the coupling between the different regions. Solar flares, coronal mass ejections, and other energetic events on the Sun create interesting and important perturbations in the near-Earth space environment. The physics of such "space weather" is central to the Journal of Atmospheric and Solar-Terrestrial Physics and the journal welcomes papers that lead in the direction of a predictive understanding of the coupled system. Regarding the upper atmosphere, the subjects of aeronomy, geomagnetism and geoelectricity, auroral phenomena, radio wave propagation, and plasma instabilities, are examples within the broad field of solar-terrestrial physics which emphasise the energy exchange between the solar wind, the magnetospheric and ionospheric plasmas, and the neutral gas. In the lower atmosphere, topics covered range from mesoscale to global scale dynamics, to atmospheric electricity, lightning and its effects, and to anthropogenic changes.