Trapping of the near‐inertial wave wakes of two consecutive hurricanes in the Loop Current

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• 作者：E. Pallàs‐Sanz ; J. Candela ; J. Sheinbaum ; J. Ochoa ; J. Jouanno
• 刊名：Journal of Geophysical Research: Oceans
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：121
• 期：10
• 页码：7431-7454
• 全文大小：4.6MB
• ISSN：2169-9291

文摘

The near-inertial trapping of the wave wakes of two consecutive hurricanes at the base of the Loop Current is described using observations of a triangular mooring array. Hurricane Gustav translates over the Loop Current twice as fast and leads to a sharper, but equally strong, wind intensity peak than Hurricane Ike. Following the passage of Gustav, near-inertial oscillations in the main thermocline have large horizontal ( <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼340±45 kmspan>span>) and vertical ( <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼850 mspan>span>) scales. The wave kinetic energy propagates down with a vertical group velocity of several tens of meters per day and leads to a downward energy flux of <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">stretchy="false">[1.82−7.10stretchy="false">]×sup>10−3sup> W sup>m−2sup>span>span>. Observations suggest that the dispersion of the wave wakes produced by the hurricanes is driven by Doppler shifting in the upper <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼600 mspan>span> and the vertical-varying vorticity inside the Loop Current. Near-inertial kinetic energy is enhanced and near-inertial oscillations are circularly polarized in a critical layer at the base of the Loop Current where the group velocity vector is nearly horizontal. The trapping and amplification of the near-inertial wave wakes of two consecutive hurricanes is addressed using a primitive equation numerical model. Numerical results suggest an increase of the near-inertial kinetic energy and vertical shear by a factor of <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">∼2span>span> near the critical layer due to wave-mean flow and wave-wave interactions. A K-profile parameterization of these interactions results in banded regions of elevated turbulent kinetic energy dissipation rates of <span data-equation-construct="true" class="math-equation-construct"><span data-equation-image="true" class="math-equation-image">span><span data-equation-mathml="true" class="math-equation-mathml" style="display:none">s:mml="http://www.w3.org/1998/Math/MathML">s:w="http://www.wiley.com/namespaces/wiley" xmlns:wiley="http://www.wiley.com/namespaces/wiley/wiley" xmlns:cr="urn://wiley-online-library/content/render" xmlns="http://www.w3.org/1998/Math/MathML">ϵ∈stretchy="false">[0.5−6.6stretchy="false">]×sup>10−6sup> W sup>m−3sup>span>span> for critical Richardson number Ri<sub>csub>&thinsp;=&thinsp;1, depending on the stratification of the water column.