Equatorial waves resolved by balloon-borne Global Navigation Satellite System radio occultation in the Strateole-2 campaign
Equatorial waves resolved by balloon-borne Global Navigation Satellite System radio occultation in the Strateole-2 campaign
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DOI：
10.5194/acp-22-15379-2022
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发表时间：
2022-12
影响因子：
6.3
通讯作者：
B. Cao;J. Haase;M. Murphy;M. Alexander;M. Bramberger;A. Hertzog
中科院分区：
文献类型：
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作者：
B. Cao;J. Haase;M. Murphy;M. Alexander;M. Bramberger;A. Hertzog
摘要。目前的气候模式难以表示实际的波浪-平均流相互作用，部分原因是人们对具有精细垂直尺度的波浪的贡献知之甚少。对这些引力波的直接观测很少，而且大多数模型都难以分辨它们。这一观测挑战无法通过卫星或稀疏的地面方法解决。stratole -2长时间平流层超压气球随水平风漂浮在等密度表面上，为广泛的时空尺度上的波浪观测提供了独特的平台。首次利用气球载全球导航卫星系统（GNSS）无线电掩星（RO）提供高垂直分辨率的赤道波观测。通过跟踪来自地平线附近GPS卫星的导航信号折射延迟，每天从气球飞行高度（~ 20公里）到6-8公里高度检索40-50个温度剖面，形成飞行轨道周围广阔区域（±400-500公里）的正交观测模式。折射率剖面与同位无线电探空仪、星载COSMIC-2 RO和再分析产品的一致性优于0.2%。200-500 m的垂直分辨率和采样的时空连续性使其能够提取垂直波长短至2-3 km的开尔文波和重力波的特性。结果表明，拉格朗日参考点与地面固定参考点的开尔文波周期（20 d vs. 16 d）存在差异，振幅与COSMIC-2相比差异高达20%，这两者都影响动量通量的估计。来自额外的伽利略、格洛纳斯和北斗星座的小数据集证明了在计划的后续活动中将采样密度增加近一倍的可行性，届时赤道全覆盖的数据将有助于更好地估计准两年一次振荡（QBO）的波浪强迫，并改进模式中的QBO表示。
Abstract. Current climate models have difficulty representing realistic wave–mean flow interactions, partly because the contribution from waves with fine vertical scales is poorly known. There are few direct observations of these waves, and most models have difficulty resolving them. This observational challenge cannot be addressed by satellite or sparse ground-based methods. The Strateole-2 long-duration stratospheric superpressure balloons that float with the horizontal wind on constant-density surfaces provide a unique platform for wave observations across a broad range of spatial and temporal scales. For the first time, balloon-borne Global Navigation Satellite System (GNSS) radio occultation (RO) is used to provide high-vertical-resolution equatorial wave observations. By tracking navigation signal refractive delays from GPS satellites near the horizon, 40–50 temperature profiles were retrieved daily, from balloon flight altitude (∼20 km) down to 6–8 km altitude, forming an orthogonal pattern of observations over a broad area (±400–500 km) surrounding the flight track. The refractivity profiles show an excellent agreement of better than 0.2 % with co-located radiosonde, spaceborne COSMIC-2 RO, and reanalysis products. The 200–500 m vertical resolution and the spatial and temporal continuity of sampling make it possible to extract properties of Kelvin waves and gravity waves with vertical wavelengths as short as 2–3 km. The results illustrate the difference in the Kelvin wave period (20 vs. 16 d) in the Lagrangian versus ground-fixed reference and as much as a 20 % difference in amplitude compared to COSMIC-2, both of which impact estimates of momentum flux. A small dataset from the extra Galileo, GLONASS, and BeiDou constellations demonstrates the feasibility of nearly doubling the sampling density in planned follow-on campaigns when data with full equatorial coverage will contribute to a better estimate of wave forcing on the quasi-biennial oscillation (QBO) and improved QBO representation in models.