Gravity wave characteristics in the Southern Hemisphere revealed by a high-resolution middle-atmosphere general circulation model
Gravity wave characteristics in the Southern Hemisphere revealed by a high-resolution middle-atmosphere general circulation model
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高分辨率中层大气环流模型揭示南半球重力波特征
DOI：
10.1175/jas-d-11-0101.1
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
and Y. Kawatani
中科院分区：
文献类型：
--
作者：
Sato K.;S. Tateno S. Watanabe;and Y. Kawatani
利用一个高分辨率中大气环流模式3年多的模拟资料，分析了南半球中高纬地区的重力波特征，不使用任何重力波参数。重力波在冬季振幅较大，主要分布在平流层中上层极涡周围区域，夏季重力波能量普遍较弱。冬季的波能分布不是纬向均匀的，但在南安第斯山脉和南极半岛有较大的下风。三维框架中的线性理论表明，垂直于波数矢量的平均风分量对地形重力波有明显的下风平流作用。射线追踪和互相关分析的结果与这一理论预期是一致的。下风向能量传播绵延数千公里，解释了冬季极涡周围重力波分布的部分原因。这一结果表明，地形重力波可以影响远离源山的水平位置的平均风。另一个有趣的特征是冬季显著的向下能量通量，这是在南安第斯山脉以南的平流层低层观察到的。向下能量通量的频率与南安第斯山脉的重力波能量呈正相关。10百帕附近静力稳定度快速增加的部分反射和/或通过非线性过程产生的重力波可能是解释向下能量通量的机制。
Gravity wave characteristics in the middle- to high-latitude Southern Hemisphere are analyzed using simulation data over 3 yr from a high-resolution middle-atmosphere general circulation model without using any gravity wave parameterizations. Gravity waves have large amplitudes in winter and are mainly distributed in the region surrounding the polar vortex in the middle and upper stratosphere, while the gravity wave energy is generally weak in summer. The wave energy distribution in winter is not zonally uniform, but it is large leeward of the southern Andes and Antarctic Peninsula. Linear theory in the three-dimensional framework indicates that orographic gravity waves are advected leeward significantly by the mean wind component perpendicular to the wavenumber vector. Results of ray-tracing and cross-correlation analyses are consistent with this theoretical expectation. The leeward energy propagation extends to several thousand kilometers, which explains part of the gravity wave distribution around the polar vortex in winter. This result indicates that orographic gravity waves can affect the mean winds at horizontal locations that are far distant from the source mountains. Another interesting feature is a significant downward energy flux in winter, which is observed in the lower stratosphere to the south of the southern Andes. The frequency of the downward energy flux is positively correlated with the gravity wave energy over the southern Andes. Partial reflection from a rapid increase in static stability around 10 hPa and/or gravity wave generation through nonlinear processes are possible mechanisms to explain the downward energy flux.