Does Ekman Friction Suppress Baroclinic Instability
Does Ekman Friction Suppress Baroclinic Instability
复制标题
艾克曼摩擦是否会抑制斜压不稳定性
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
R. Pierrehumbert
中科院分区：
文献类型：
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作者：
Shian‐Jiann Lin;R. Pierrehumbert
摘要 为了解决法雷尔提出的关于大气中是否存在简正模态不稳定性的问题，重新检验了埃克曼摩擦力对斜压不稳定性的影响。由于经向约束程度是结果的核心，因此使用线性化二维（纬度-高度）准地转模型来消除在一维（仅垂直剪切）模型中选择通道宽度所固有的任意性。二维特征值问题通过伪谱方法在垂直和经向方向上使用有理切比雪夫展开来解决。结果表明，只有强埃克曼摩擦力与弱大范围风切变相结合才能消除不稳定。基于现实边界层模型的埃克曼摩擦力估计表明，当边界层呈中性分层时，这种情况可能会优于陆地。对于适合开放海洋的埃克曼摩擦力值，摩擦力可以降低...的增长率
Abstract The effect of Ekman friction on baroclinic instability is reexamined in order to address questions raised by Farrell concerning the existence of normal mode instability in the atmosphere. As the degree of meridional confinement is central to the result, a linearized two-dimensional (latitude-height) quasi-geostrophic model is used to obviate the arbitrariness inherent in choosing a channel width in one-dimensional (vertical shear only) models. The two-dimensional eigenvalue problem was solved by pseudospectral method using rational Chebyshev expansions in both vertical and meridional directions. It is concluded that the instability can be eliminated only by the combination of strong Ekman friction with weak large-scale wind shear. Estimates of Ekman friction based on a realistic boundary-layer model indicate that such conditions can prevail over land when the boundary layer is neutrally stratified. For values of Ekman friction appropriate to the open ocean, friction can reduce the growth rate of ...