The South Georgia Wave Experiment ( SG-WEX ): radiosonde observations of gravity waves in the lower stratosphere. Part I: Energy density, momentum flux and wave propagation direction
The South Georgia Wave Experiment ( SG-WEX ): radiosonde observations of gravity waves in the lower stratosphere. Part I: Energy density, momentum flux and wave propagation direction
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南乔治亚波实验（SG-WEX）：无线电探空仪观测平流层下部的重力波。
DOI：
10.1002/qj.3181
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发表时间：
2017
影响因子：
8.9
通讯作者：
Moffat-Griffin T
中科院分区：
文献类型：
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作者：
Moffat-Griffin T
重力波在整个大气层的能量和动量传输中发挥着至关重要的作用。有人认为，位于强风地区的小山岛可能会产生大量的这些波浪。这种通量很重要，因为这些岛屿在全球环流模型中没有得到很好的解决。因此，需要确定这些岛屿产生的重力波的大小和变化：南乔治亚岛（南纬 54°，西经 37°）拥有这些岛屿中最高的山脉。在这里，我们提出了无线电探空仪在南乔治亚岛测量到的重力波的第一份报告。这些测量是在南乔治亚波实验 (SG-WEX) 的两次密集活动中进行的，这是一项调查南乔治亚岛上空重力波的多仪器和建模活动。 2015 年举行了两次密集的无线电探空仪活动，一次在 1 月，一次在 6 月/7 月，总共成功发射 89 次。我们利用这些新的观测结果来确定平流层下部的重力波特性。夏季活动观察到平均波浪能量密度（动能+势能+垂直）为3.6 J kg−1，平均赝动量通量为2.3 mPa。在冬季活动中，观测到的值更大：平均波浪能量密度为 8.4 J kg−1，平均赝动量通量为 8.7 mPa。引人注目的是，分析表明，冬季 66% 的波浪向下传播；在夏季，只有 8% 的人这样做。这些结果表明冬季平流层中可能存在额外的波源。我们认为，夏季和冬季活动期间观察到的波浪特性之间的差异是由于多种因素的复杂组合造成的，包括表面风条件的差异（与地形波的产生有关）、风暴频率和极地平流层急流的接近程度。这些结果表明冬季南乔治亚岛上空重力波活动大幅增加。
Gravity waves play a critical role in the transport of energy and momentum throughout the atmosphere. It has been suggested that small mountainous islands located in regions of strong winds may generate significant fluxes of these waves. Such fluxes would be important because these islands are not well resolved in global circulation models. Thus, there is a need to determine the magnitude and variability of gravity waves generated from such islands: South Georgia (54°S, 37°W) has the highest mountains of these islands. Here, we present the first report of gravity waves measured by radiosondes over South Georgia. The measurements were made in two intensive campaigns as part of the South Georgia Wave EXperiment (SG‐WEX), a multi‐instrument and modelling campaign investigating gravity waves above South Georgia. The two intensive radiosonde campaigns were held in 2015, one in January and one in June/July, totalling 89 successful launches. We use these new observations to determine gravity‐wave properties in the lower stratosphere. The summer campaign observed an average wave energy density (kinetic + potential + vertical) of 3.6 J kg−1and an average pseudo‐momentum flux of 2.3 mPa. In the winter campaign the values observed were larger: an average wave energy density of 8.4 J kg−1and an average pseudo‐momentum flux of 8.7 mPa. Strikingly, analysis reveals that in winter 66% of waves were propagating downwards; in summer only 8% did so. These results suggest that there may be additional sources of waves in the winter stratosphere. We propose that the differences between wave properties observed during the summer and winter campaigns are due to a complex combination of factors including differences in surface wind conditions (linked to orographic wave generation), frequency of storms and the proximity of the polar stratospheric jet. These results demonstrate a large increase in gravity‐wave activity in winter above South Georgia.