Simulation and Scaling of the Turbulent Vertical Heat Transport and Deep-Cycle Turbulence across the Equatorial Pacific Cold Tongue
Simulation and Scaling of the Turbulent Vertical Heat Transport and Deep-Cycle Turbulence across the Equatorial Pacific Cold Tongue
复制标题
赤道太平洋冷舌湍流垂直热传输和深循环湍流的模拟和缩放
DOI：
10.1175/jpo-d-21-0153.1
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发表时间：
2022
影响因子：
3.5
通讯作者：
Moum, J. N.
中科院分区：
文献类型：
--
作者：
Whitt, D. B.;Cherian, D. A.;Holmes, R. M.;Bachman, S. D.;Lien, R.-C.;Large, W. G.;Moum, J. N.
太平洋冷舌的微观结构观察表明，湍流经常渗透到温跃层，在夜间和清晨产生每平方米数百瓦的向下热传输。然而，实际上对这种深循环湍流 (DCT) 的所有观测均来自 0°、140°W。这里，海洋过程模拟的层次结构，包括嵌入区域模型中的允许亚尺度的区域模型和允许湍流的大涡模拟 (LES)，提供了对 0°、140°W 及以上的混合和 DCT 的深入了解。区域后报量化了1999年至2016年整个冷舌地下湍流热通量的时空变化。平均地下湍流通量在赤道2°范围内最强（∼100 W m−2），整个冷舌北半球略强（∼10 W m−2），并与地表热通量相关（r2 = 0.7）。地下热通量的季节周期与地表热通量不共变，范围从赤道附近的 150 W m−2 到 4°N 和 4°S 处的 30 和 10 W m−2。地下热通量的季节变化呈对数分布，与时间平均通量在空间上协变，并在北纬 0° 和 3°、西经 140° 的北方秋季 34 天 LES 中突出显示。强烈的 DCT 在 0° 的暗流上方频繁发生，在 3°N 时间歇性发生。日平均热通量与体垂直切变和风应力成比例，它们共同解释了两个 LES 中约 90% 的日方差。对 0°、140°W 的缩放比例的观测验证令人鼓舞，但需要超过 0°、140°W 的观测，以促进海洋模型中混合参数化的细化。意义声明这项工作是对广泛社区努力的根本性贡献，旨在改进用于季节性到长期预测的全球长期天气和气候预报模型。季节性时间尺度的大部分可预测性源自赤道上东太平洋在厄尔尼诺和拉尼娜条件之间变化的缓慢演变。这项研究提出了最先进的赤道东太平洋海洋湍流和混合的高分辨率区域数值模拟。研究结果为未来的实地工作规划以及未来在全球预测模型中完善海洋混合表示的努力提供了信息。
Microstructure observations in the Pacific cold tongue reveal that turbulence often penetrates into the thermocline, producing hundreds of watts per square meter of downward heat transport during nighttime and early morning. However, virtually all observations of this deep-cycle turbulence (DCT) are from 0°, 140°W. Here, a hierarchy of ocean process simulations, including submesoscale-permitting regional models and turbulence-permitting large-eddy simulations (LES) embedded in a regional model, provide insight into mixing and DCT at and beyond 0°, 140°W. A regional hindcast quantifies the spatiotemporal variability of subsurface turbulent heat fluxes throughout the cold tongue from 1999 to 2016. Mean subsurface turbulent fluxes are strongest (∼100 W m−2) within 2° of the equator, slightly (∼10 W m−2) stronger in the northern than Southern Hemisphere throughout the cold tongue, and correlated with surface heat fluxes (r2= 0.7). The seasonal cycle of the subsurface heat flux, which does not covary with the surface heat flux, ranges from 150 W m−2near the equator to 30 and 10 W m−2at 4°N and 4°S, respectively. Aseasonal variability of the subsurface heat flux is logarithmically distributed, covaries spatially with the time-mean flux, and is highlighted in 34-day LES of boreal autumn at 0° and 3°N, 140°W. Intense DCT occurs frequently above the undercurrent at 0° and intermittently at 3°N. Daily mean heat fluxes scale with the bulk vertical shear and the wind stress, which together explain ∼90% of the daily variance across both LES. Observational validation of the scaling at 0°, 140°W is encouraging, but observations beyond 0°, 140°W are needed to facilitate refinement of mixing parameterization in ocean models.Significance StatementThis work is a fundamental contribution to a broad community effort to improve global long-range weather and climate forecast models used for seasonal to longer-term prediction. Much of the predictability on seasonal time scales is derived from the slow evolution of the upper eastern equatorial Pacific Ocean as it varies between El Niño and La Niña conditions. This study presents state-of-the-art high-resolution regional numerical simulations of ocean turbulence and mixing in the eastern equatorial Pacific. The results inform future planning for field work as well as future efforts to refine the representation of ocean mixing in global forecast models.