Near-Inertial Wave Wake of Hurricanes Katrina and Rita over Mesoscale Oceanic Eddies
Near-Inertial Wave Wake of Hurricanes Katrina and Rita over Mesoscale Oceanic Eddies
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DOI：
10.1175/2010jpo4309.1
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发表时间：
2010-06-01
影响因子：
3.5
通讯作者：
Shay, Lynn K.
中科院分区：
文献类型：
--
作者：
Jaimes, Benjamin;Shay, Lynn K.
热带气旋卡特里娜（Katrina）和丽塔（Rita）作为主要飓风在墨西哥湾高能地转海洋特征上空移动。在两个风暴经过气旋和反气旋地转相对涡度zeta(g)后，测量到海洋混合层（OML）冷却分别增加和减少。本文根据地转涡旋中风暴近惯性波尾迹的演变来研究这种对比热响应。实际地转流中的观测数据和射线追踪技术表明，tc强迫的OML近惯性波被困在负zeta(g)区域，在那里它们迅速传播到温跃层。由于近惯性能量的快速向下弥散减少了可用于增加OML底部垂直剪切的动能，因此这些反气旋旋转状态与OML冷却减少的分布相吻合。相比之下，tc强迫的OML近惯性波在气旋环流的上层停滞，这加强了垂直切变和夹带冷却。在与卡特里娜相互作用的地转气旋内部，上升的近惯性能量传播占主导地位；这些向上传播波的显著特征是：(1)由于上升流-下升流过程的地转调整，它们是从海洋内部辐射出来的；（ii）在向上传播过程中，当遇到f + zeta(g)/2的值增加时，它们会水平放大，而不是随着浮力频率的增加；（iii）它们通过在OML下面的一个关键层的剪切不稳定产生了间歇性的垂直混合。为了改进对tc诱导的OML冷却的预测，模式必须捕捉地转特征，湍流闭包必须代表近惯性波过程，如OML基底和温跃层之间的弥散和断裂。
Tropical cyclones (TCs) Katrina and Rita moved as major hurricanes over energetic geostrophic ocean features in the Gulf of Mexico. Increased and reduced oceanic mixed layer (OML) cooling was measured following the passage of both storms over cyclonic and anticyclonic geostrophic relative vorticity zeta(g), respectively. This contrasting thermal response is investigated here in terms of the evolution of the storms' near-inertial wave wake in geostrophic eddies. Observational data and ray-tracing techniques in realistic geostrophic flow indicate that TC-forced OML near-inertial waves are trapped in regions of negative zeta(g), where they rapidly propagate into the thermocline. These anticyclonic-rotating regimes coincided with the distribution of reduced OML cooling because rapid downward dispersion of near-inertial energy reduced the amount of kinetic energy available to increase vertical shears at the OML base. By contrast, TC-forced OML near-inertial waves were stalled in upper layers of cyclonic circulations, which strengthened vertical shears and entrainment cooling. Upgoing near-inertial energy propagation dominated inside a geostrophic cyclone that interacted with Katrina; the salient characteristics of these upward-propagating waves were the following: (i) they were radiated from the ocean interior because of geostrophic adjustment following upwelling-downwelling processes; (ii) rather than with the buoyancy frequency, they amplified horizontally as they encountered increasing values of f + zeta(g)/2 during upward propagation; and (iii) they produced episodic vertical mixing through shear instability at a critical layer underneath the OML. To improve the prediction of TC-induced OML cooling, models must capture geostrophic features and turbulence closures must represent near-inertial wave processes such as dispersion and breaking between the OM L base and the thermocline.