Transient eastward-propagating long-period waves observed over the South Pole
Transient eastward-propagating long-period waves observed over the South Pole
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在南极上空观测到的瞬态向东传播的长周期波
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
E. Merzlyakov
中科院分区：
文献类型：
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作者：
S. Palo;Y. Portnyagin;J. Forbes;N. Makarov;E. Merzlyakov
1995年利用流星雷达对南极的水平风场进行了观测。这些数据揭示了南极上空存在着丰富的波谱，具有明显的年度发生。在这个频谱中包括周期大于一个太阳日的长周期波，这些波正在向东传播。这些波动表现出明显的季节性发生，其中波动周期的包络从秋分附近的10天周期减少到冬至附近的最小2天周期，然后在春分时向近10天的周期发展。对准地转位涡经向梯度的计算表明，在高纬度中上层有一个区域可以支持不稳定，并作为这些波的来源。对该区域不稳定可能产生的波浪周期的估计与南极上空观测到的波浪周期的季节变化非常相似。这些结果与南极上空观测到的向东传播的长周期波是由极地上层中间层不稳定产生的假设相一致。然而，考虑到我们有限的数据集，我们不能排除平流层来源的可能性。在南半球冬季，这一向东传播的波谱中嵌入了许多不同的波事件。使用恒定Q滤波器组，已经识别和定位了8个这样的波事件。这些波事件的周期从1.7天到9.8天不等，都至少存在3个波周期。最小二乘分析表明，其中一些事件与沿地理极点沿纬向传播的波不一致，可能与围绕偏离地理极点的动力极点传播的波有关。此外，观察到的一个事件似乎是站立振荡。
Observations of the horizontal wind field over the South Pole were made during 1995 using a meteor radar. These data have revealed the presence of a rich spectrum of waves over the South Pole with a distinct annual occurrence. Included in this spectrum are long-period waves, whose periods are greater than one solar day, which are propagating eastward. These waves exhibit a distinct seasonal occurrence where the envelope of wave periods decreases from a period of 10 days near the fall equinox to a minimum of 2 days near the winter solstice and then progresses towards a period near 10 days at the spring equinox. Computation of the meridional gradient of quasi-geostrophic potential vorticity has revealed a region in the high-latitude upper mesosphere which could support an instability and serve as a source for these waves. Estimation of the wave periods which would be generated from an instability in this region closely resembles the observed seasonal variation in wave periods over the South Pole. These results are consistent with the hypothesis that the observed eastward propagating long-period waves over the South Pole are generated by an instability in the polar upper mesosphere. However, given our limited data set we cannot rule out a stratospheric source. Embedded in this spectrum of eastward propagating waves during the austral winter are a number of distinct wave events. Eight such wave events have been identified and localized using a constant-Q filter bank. The periods of these wave events ranges from 1.7 to 9.8 days and all exist for at least 3 wave periods. Least squares analysis has revealed that a number of these events are inconsistent with a wave propagating zonally around the geographic pole and could be related to waves propagating around a dynamical pole which is offset from the geographic pole. Additionally, one event which was observed appears to be a standing oscillation.