The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO
The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO
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DOI：
10.5194/acp-15-7797-2015
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发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Mitchell, N. J.
中科院分区：
文献类型：
--
作者：
Hindley, N. P.;Wright, C. J.;Mitchell, N. J.
几乎所有的大气环流模式都不能很好地再现南方冬季极涡的观测行为。有人认为，这些偏差是由于低估了S 60度附近的重力波对大气的阻力，特别是在南安第斯山脉和南极半岛上空强烈重力波通量的“热点”附近。在这里，我们使用来自宇宙卫星星座的全球定位系统无线电掩星(GPS-RO)数据来确定热点内外的重力波的特性。我们显示了相当大的向南传播到S 60度附近的纬度，显然是在南安第斯山脉上产生的波。我们认为，这种传播可能解释了模型中缺失的波阻的很大一部分原因。此外，还有一个长长的背风区，重力波能量增加，从山脉向东扫过南大洋。尽管该地区具有惊人的性质，但从历史上看，它的来源很难确定。我们的观测表明，这一区域既包括局部产生的波，也包括从热点顺风向平流的地形波。我们描述并使用了一种新的基于小波的分析技术，用于从宇宙温度分布中定量识别单个波。这一分析揭示了南大洋波浪场中不同的波幅和短时间尺度变化的地理机制。最后，我们使用2006年宇宙星座部署阶段增加的近距离分布对的数量来估计重力波的水平波长。结果表明，在充分观测的情况下，GPS-RO可以对热点区域的平流层重力波动量通量进行物理上合理的估计，并与其他方法的测量结果相一致。我们在以前的卫星和模型研究的背景下讨论了我们的结果，并解释了它们如何促进我们对南部平流层波动的性质和起源的理解。
Nearly all general circulation models significantly fail to reproduce the observed behaviour of the southern wintertime polar vortex. It has been suggested that these biases result from an underestimation of gravity wave drag on the atmosphere at latitudes near 60 degrees S, especially around the "hot spot" of intense gravity wave fluxes above the mountainous Southern Andes and Antarctic peninsula. Here, we use Global Positioning System radio occultation (GPS-RO) data from the COSMIC satellite constellation to determine the properties of gravity waves in the hot spot and beyond. We show considerable southward propagation to latitudes near 60 degrees S of waves apparently generated over the southern Andes. We propose that this propagation may account for much of the wave drag missing from the models. Furthermore, there is a long leeward region of increased gravity wave energy that sweeps eastwards from the mountains over the Southern Ocean. Despite its striking nature, the source of this region has historically proved difficult to determine. Our observations suggest that this region includes both waves generated locally and orographic waves advected downwind from the hot spot. We describe and use a new wavelet-based analysis technique for the quantitative identification of individual waves from COSMIC temperature profiles. This analysis reveals different geographical regimes of wave amplitude and short-timescale variability in the wave field over the Southern Ocean. Finally, we use the increased numbers of closely spaced pairs of profiles from the deployment phase of the COSMIC constellation in 2006 to make estimates of gravity wave horizontal wavelengths. We show that, given sufficient observations, GPS-RO can produce physically reasonable estimates of stratospheric gravity wave momentum flux in the hot spot that are consistent with measurements made by other techniques. We discuss our results in the con-text of previous satellite and modelling studies and explain how they advance our understanding of the nature and origins of waves in the southern stratosphere.