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首页> 外文期刊>Journal of Physical Oceanography >Destruction of Potential Vorticity by Winds
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Destruction of Potential Vorticity by Winds

机译：风对潜在涡旋的破坏

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The destruction of potential vorticity (PV) at ocean fronts by wind stress-driven frictional forces is examined using PV flux formalism and numerical simulations. When a front is forced by "downfront" winds, that is, winds blowing in the direction of the frontal jet, a nonadvective frictional PV flux that is upward at the sea surface is induced. The flux extracts PV out of the ocean, leading to the formation of a boundary layer thicker than the Ekman layer, with nearly zero PV and nonzero stratification. The PV reduction is not only active in the Ekman layer but is transmitted through the boundary layer via secondary circulations that exchange low PV from the Ekman layer with high PV from the pycnocline. Extraction of PV from the pycnocline by the secondary circulations results in an upward advective PV flux at the base of the boundary layer that scales with the surface, nonadvective, frictional PV flux and that leads to the deepening of the layer. At fronts forced by both downfront winds and a destabilizing atmospheric buoyancy flux F_(atm)~B, the critical parameter that determines whether the wind or the buoyancy flux is the dominant cause for PV destruction is (H/δ_e)(F_(wind)~B/F_(atm)~B), where H and δ_e are the mixed layer and Ekman layer depths, F_(wind)~B = S~2τ_o/(ρ_of), S~2 is the magnitude of the lateral buoyancy gradient of the front, τ_o is the downfront component of the wind stress, ρ_o is a reference density, and f is the Coriolis parameter. When this parameter is greater than 1, PV destruction by winds dominates and may play an important role in the formation of mode water.
机译：使用PV通量形式和数值模拟研究了风应力驱动的摩擦力对洋锋潜在涡度（PV）的破坏。当前风被“后风”强迫时，也就是说，风向着正面射流的方向吹动时，会引起在海面向上的非平流摩擦PV通量。磁通量将PV抽出海洋，导致形成比Ekman层厚的边界层，PV几乎为零，分层为非零。 PV降低不仅在Ekman层中有效，而且还通过次级循环传输通过边界层，该次级循环将Ekman层的低PV与比多菌灵的高PV交换。通过次级循环从比多菌灵中提取PV会导致边界层底部的对流PV通量随表面，非对流，摩擦PV通量成比例增加，并导致该层的加深。在前风和不稳定的大气浮力通量F_（atm）〜B共同作用的前沿，决定风或浮力通量是造成PV破坏的主要原因的关键参数是（H /δ_e）（F_（wind） 〜B / F_（atm）〜B），其中H和δ_e是混合层和埃克曼层的深度，F_（wind）〜B = S〜2τ_o/（ρ_of），S〜2是横向浮力梯度的大小正面的τ_o是风应力的下部分量，ρ_o是参考密度，f是科里奥利参数。当此参数大于1时，风对PV的破坏占主导，并且可能在模式水的形成中起重要作用。

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