Upgradient and downgradient potential vorticity fluxes produced by forced Rossby waves Part II: Parameter sensitivity and physical interpretation
Upgradient and downgradient potential vorticity fluxes produced by forced Rossby waves Part II: Parameter sensitivity and physical interpretation
复制标题
受迫罗斯贝波产生的上升和下降位涡通量第二部分：参数敏感性和物理解释
DOI：
10.1175/jpo-d-17-0198.1
复制
发表时间：
2018
影响因子：
3.5
通讯作者：
Genta Mizuta
中科院分区：
文献类型：
--
作者：
Genta Mizuta
我们研究了在两层准地转模型中由强迫罗斯比波产生的位涡（PV）通量，使用摄动分析。罗斯比波是由施加在上层的外力激发的。向南的PV通量是由非线性波波相互作用激发的高阶罗斯比波在低层产生的，而向北的PV通量是在上层产生的。PV通量的方向与前人研究的风力环流涡旋分解模式的结果一致。与涡旋解析模型相比，向南的PV通量在较宽的参数范围内产生。即使在弱分层的极限下，PV通量的基本特征也保持不变。在这个极限下，除了使下层不受外部强迫的直接影响外，分层对流动几乎没有影响。向南的PV通量的机制是用正压罗斯比波的基本特征来解释的，而不依赖于模型的细节。此外，罗斯比波的共振三重相互作用不影响PV通量。分层会减弱或增强PV通量，这取决于外强迫的水平尺度。
We examine the potential vorticity (PV) flux produced by forced Rossby waves in a two-layer quasigeostrophic model, using a perturbation analysis. Rossby waves are excited by external forcing applied to the upper layer. The southward PV flux is produced in the lower layer by the higher-order Rossby waves that are excited by nonlinear wave–wave interactions, whereas the northward PV flux is produced in the upper layer. The direction of the PV flux is consistent with that obtained by an eddy-resolving model of the wind-driven circulation in previous studies. The southward PV flux is produced in a wide parameter range comparable to the eddy-resolving model. The basic features of the PV flux remain unchanged even in the limit of weak stratification. In this limit, stratification has nearly no effect on the flow, except that it isolates the lower layer from the direct effects of external forcing. The mechanism of the southward PV flux is explained using basic features of the barotropic Rossby waves and does not depend on details of the model. Furthermore, the resonant triad interaction of Rossby waves does not affect the PV flux. Stratification weakens or strengthens the PV flux depending on the horizontal scale of the external forcing.