热带平流层是通往全球平流层的门户，也是太阳能地球工程的常用地点。人们对这个遥远而难以观测的区域的动力学，特别是在湍流长度尺度上，了解得很少。现有对湍流频率和强度的观测估计差异很大。此外，湍流的来源以及湍流与平均流之间的关系，在很大程度上是未知的。
研究团队从来自两个海洋盆地的四个赤道站点，建立了一个21y的高垂直分辨率（10m）无线电探空数据数据库，以研究热带平流层湍流的频率、变率和来源。研究人员以亚临界Richardson数作为湍流的代表，以识别厚度超过200m的湍流层。研究发现，热带平流层的湍流部分受到准两年一次振荡（QBO）的强烈调节。
在QBO相移期间，湍流会增强，在QBO相从负向正转换之前，大气的湍流最为严重，其中湍流不稳定性通常发生在开尔文波的特定相内。当QBO相位建立时，湍流不太常见，而在QBO负相期间。大气湍流最小。赤道平流层下层的湍流分数随QBO相位的变化而变化10倍以上。这种关系为该区域的多尺度动力学，提供了一个精确的观测约束，这对于评估大气模式、研究QBO背景下的波均流相互作用，以及为平流层飞行器的运行和地球工程气溶胶的注入提供了信息。
附：英文原文
Title: Turbulence in the tropical stratosphere, equatorial Kelvin waves, and the quasi-biennial oscillation
Author: Atlas, Rachel, Podglajen, Aurélien, Wilson, Richard, Hertzog, Albert, Plougonven, Riwal
Issue&Volume: 2025-1-8
Abstract: The tropical stratosphere is the gateway to the global stratosphere and a commonly proposed location for solar geoengineering. The dynamics of this remote and difficult to observe region are poorly understood, particularly at turbulent length scales. Existing observational estimates of turbulence frequency and strength vary widely. Furthermore, the sources of turbulence and the relationship between turbulence and the mean flow are largely unknown. We assembled a 21-y database of high vertical resolution (10 m) radiosonde data from four equatorial sites in two ocean basins to study tropical stratospheric turbulence frequency, variability, and sources. Turbulent layers thicker than 200 m are identified using subcritical Richardson number as a proxy for turbulence. We show that the turbulent fraction of the tropical stratosphere is strongly modulated by the quasi-biennial oscillation (QBO). Turbulence is enhanced during the QBO phase shifts, and the atmosphere is most turbulent right before the QBO phase switches from negative to positive, where turbulent instabilities typically occur within specific phases of Kelvin waves. Turbulence is less common when the QBO phase is well established, and the atmosphere is least turbulent during the negative phase of the QBO. The turbulent fraction of the equatorial lower stratosphere varies over a factor of ten depending on QBO phase. This relationship provides a robust observational constraint on the multiscale dynamics within this region, which is useful for evaluating atmospheric models, studying wave-mean flow interactions in the context of the QBO, and informing the operation of stratospheric aircraft and the injection of aerosol for geoengineering.
DOI: 10.1073/pnas.2409791122
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2409791122