التفاصيل البيبلوغرافية
| العنوان: |
Parameterization of the Vertical Mixing for the Luzon Undercurrent in the Northern Western Pacific Ocean. |
| المؤلفون: |
Chen, Xianliang, Gan, Jianping, Hui, Chiwing, McWilliams, James C. |
| المصدر: |
Journal of Geophysical Research. Oceans; Nov2024, Vol. 129 Issue 11, p1-20, 20p |
| مصطلحات موضوعية: |
VERTICAL mixing (Earth sciences), RICHARDSON number, PHYSICS experiments, OCEAN, PHYSICS |
| مستخلص: |
The Luzon Undercurrent (LUC) is one of the most significant western boundary undercurrents in the northern western Pacific Ocean (WPO), essential for subsurface water transport and connecting subtropical–equatorial circulations. Over the last three decades, abundant observational progress has been made in revealing the basic features of the LUC. However, the dynamics and thus successful modeling of the LUC remain unresolved. In this work, we conducted a high‐resolution (3 km, 60 levels) numerical investigation of the WPO circulation using the China sea multi‐scale ocean modeling system. We paid particular attention to the vertical mixing, aiming to reasonably resolve the LUC by modifying the vertical mixing parameterization. Based on physics reasoning and experiments of physically based modeling, we designed an adaptive mixing scheme (AMS), which used a Munk‐like function in the thermocline for enhanced vertical mixing in the areas of small Richardson numbers. Using the AMS, we reproduced the two‐layer WPO circulations well and captured the inshore component of the LUC consistent with observations. Furthermore, we studied the dynamics of the LUC by analyzing the momentum balance and found that the LUC is primarily maintained by baroclinic pressure gradient force due to strong thermocline tilting near the western boundary. Enhanced vertical mixing in this highly sheared region crucially provides sufficient geostrophic support to sustain the LUC. Also, nonlinearity and submesoscale motions contribute positively to the LUC. This work advances physical understanding of the current‐undercurrent system and improves numerical capability in capturing the LUC and WPO circulations. Plain Language Summary: In the northern western Pacific Ocean (WPO), there exists complex undercurrents below the upper layer (depth ∼500–1,500 m), which flow in the opposite direction from the strong circulation in the upper ocean (depth <∼500 m). The undercurrents are significant for subsurface transport and connecting subtropical‐equatorial circulations; together with the upper circulation, they form the WPO circulation system. The undercurrents are less understood and their underlying physics remains unclear. In this study, we investigate the Luzon Undercurrent (LUC), which flows southward beneath the northward Kuroshio to the east coast off Luzon Island. Abundant observational works have unveiled the characteristics of the LUC, but little attention was paid to its dynamics. So far, the LUC is poorly resolved in prevailing global/regional ocean models. In this work, we developed an adaptive mixing scheme based on physics reasoning and modeling experiments, such that the LUC physics can be resolved and well reproduced in our regional model. Furthermore, we revealed the dynamics of the LUC and summarized key factors to its formation and maintenance. This work advances our physical understanding toward the undercurrents and improves numerical capability in simulating the LUC and WPO circulations. Key Points: Baroclinic pressure gradient force due to strong isopycnal tilting in the thermocline is crucial to the formation and maintenance of the Luzon Undercurrent (LUC)The strong isopycnal tilting is induced by locally enhanced vertical mixing. Nonlinearity and submesoscales also benefit the LUC formationA Munk‐like adaptive mixing scheme is designed to capture the LUC, providing significant improvement over previous results [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
Complementary Index |