Meridional propagation of planetary-scale waves in vertical shear: Implication for the Venus atmosphere
Meridional propagation of planetary-scale waves in vertical shear: Implication for the Venus atmosphere
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DOI：
10.1175/jas3684.1
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发表时间：
2006-06-01
影响因子：
3.1
通讯作者：
Imamura, Takeshi
中科院分区：
文献类型：
--
作者：
Imamura, Takeshi
结果表明，行星尺度波固有地伴随着纬向动量输送时，他们垂直传播的垂直剪切纬向流。由于波的纬度尺度依赖于内在的相速度，正（负）垂直切变应迫使逆（逆行）波集中赤道和逆行（逆）波扩大极向上传播的过程中。因此，Eliassen-Palm（EP）通量矢量从垂直方向14倾斜，出现非零纬度动量通量。无论纬向传播方向如何，动量传输的方向在正（负）垂直剪切中始终应该是向赤道（向极）的。这个想法被应用于金星中层大气中向上传播的波，那里存在强中纬度喷流的垂直剪切和赤道超旋转。数值结果表明，Kelvin和Elderde惯性重力波向赤道方向聚焦，混合Rossby重力波和Rossby波在云顶以下向极向扩展。前者主要归因于超旋转的垂直切变，而后者主要归因于中纬度急流下方的垂直切变。行星尺度波的这种特征将导致高纬度和低纬度之间的角动量分离，并且至少部分地有助于维持超旋转。
It is shown that planetary-scale waves are inherently accompanied by latitudinal momentum transport when they propagate vertically in vertically sheared zonal flows. Because of the dependence of the wave's latitudinal scale on the intrinsic phase speed, positive (negative) vertical shear should force prograde (retrograde) waves to focus equatorward and retrograde (prograde) waves to expand poleward in the course of upward propagation. Consequently, Eliassen-Palm (EP) flux vectors are tilted from the vertical 14 and nonzero latitudinal momentum fluxes occur. The direction of momentum transport should always be equatorward (poleward) in positive (negative) vertical shear irrespective of the zonal propagation direction.The idea was applied to upwardly propagating waves in the Venusian middle atmosphere, where vertical shear of strong midlatitude jets and equatorial superrotation exist. Numerical solutions showed that Kelvin and prograde inertio-gravity waves focus equatorward and mixed Rossby-gravity and Rossby waves expand poleward below the cloud top. The former is attributed primarily to the vertical shear of the superrotation, while the latter to the vertical shear beneath the midlatitude jets. Such characteristics of planetary-scale waves will cause angular momentum separation between high and low latitudes and, at least partly, contribute to the maintenance of the superrotation.