Turbulence, Richardson number (Ri) distributions, and parametric instabilities in the turbopause region (96–105 km) from Na LIDAR measurements at the Andes Lidar Observatory (ALO)

IF 1.8 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Journal of Atmospheric and Solar-Terrestrial Physics Pub Date : 2024-07-20 DOI:10.1016/j.jastp.2024.106313

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Abstract

Turbulence in the Mesosphere and Lower Thermosphere (MLT) region is responsible for vertical mixing and transport of constituents and heat and the formation of the turbo-pause. A study of turbulence at the Andes Lidar Observatory (ALO) by Philbrick et al. (2021) found, for 25 nights of lidar observations, the probability of Ri < 1/4 decreased with altitude above 100 km, whereas the power in turbulence increased. The objective of this study is to understand the atmospheric process responsible for the observed increase in turbulence power with altitude. Conventionally turbulence is caused by instabilities due to convection (Ri < 0), and Kelvin-Helmholtz Instabilities (KHI), 0 < Ri < 1/4. These criteria are based on laminar flow, a waveless basic state. However, wave-modulated states requiring Floquet theory may dominate the MLT region and can generate instabilities and turbulence under more stable conditions (Ri > 1/4, Klostermeyer, 1990). It was determined in this study the probability of Ri > 1/4 to be >70% at 105 km, consistent with parametric instability (PI) where large tidal induced wind shears and gravity wave presence are contributing factors.

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从安第斯激光雷达观测站 (ALO) 的激光雷达测量中获得的湍流、理查德森数 (Ri) 分布以及湍流顶区域（96-105 公里）的参数不稳定性。

中间层和下热层（MLT）区域的湍流是成分和热量垂直混合和传输以及涡轮停顿形成的原因。Philbrick 等人（2021 年）在安第斯激光雷达观测站（ALO）进行的湍流研究发现，在 25 个夜间的激光雷达观测中，Ri < 1/4 的概率随着高度超过 100 公里而降低，而湍流的功率却在增加。本研究的目的是了解导致观测到的湍流功率随高度增加的大气过程。传统的湍流是由对流引起的不稳定（Ri < 0）和开尔文-赫尔姆霍兹不稳定（KHI）（0 < Ri < 1/4 ）引起的。这些标准基于层流这种无波基本状态。然而，需要采用 Floquet 理论的波调制状态可能在 MLT 区域占主导地位，并可能在更稳定的条件下产生不稳定性和湍流（Ri > 1/4, Klostermeyer, 1990）。本研究确定，在 105 千米处 Ri > 1/4 的概率为 70%，与参数不稳定性（PI）一致，其中大潮汐诱导的风切变和重力波的存在是诱因。

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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.