This study examines variations through the year in the rate of descent of the quasi‐biennial oscillation (QBO) wind in the tropical lower stratosphere. The work is based on the Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2) multiyear global reanalysis. A 10‐member ensemble of free‐running atmospheric simulations using the Global Earth Observing System (GEOS) atmospheric general circulation model is also examined. The QBO winds are decomposed into two orthogonal modes that describe amplitude and phase propagation. This reveals a semiannual signal in descent rate, with slow descent at times of large middle‐latitude planetary wave activity, suggesting that this wave activity influences equatorial vertical velocity. This result also explains the suppression of QBO wind transitions during active wave times. Results also show a variation in descent speed when plotted against QBO phase. These results provide a baseline of QBO behavior for future QBO modeling.

中文翻译：

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准两年一次振荡下降的季节变化

这项研究调查了热带低平流层中准双年度振荡（QBO）风的下降速率在一年中的变化。这项工作基于研究和应用的现代时代回顾分析，版本2（MERRA-2）多年全球重新分析。还研究了使用全球地球观测系统（GEOS）大气总循环模型的10人自由运行大气模拟合奏。QBO风被分解为两个正交模式，分别描述振幅和相位传播。这揭示了每半年一次的下降信号，在中纬度大的行星波活动时下降缓慢，这表明该波活动影响着赤道垂直速度。该结果还解释了在活动波时间内抑制QBO风向的转变。当相对于QBO相位作图时，结果还显示下降速度的变化。这些结果为将来的QBO建模提供了QBO行为的基线。