Scaling the Diurnal Mixing/Mixed Layer Depth in the Tropical Ocean: A Case Study in the South China Sea

doi:10.1029/2024JC021296

IOCAS-IR > 海洋环流与波动重点实验室

	Scaling the Diurnal Mixing/Mixed Layer Depth in the Tropical Ocean: A Case Study in the South China Sea
	Cao, Zhiyong 1,2,3,4; Liu, Zhiyu 1,2; Wang, Dong 1,2; Wang, Jianing3,4 ; Lin, Hongyang 1,2; Zhang, Fangtao 1,2
	2024-09-01
发表期刊	JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN	2169-9275
卷号	129 期号:9 页码:16
通讯作者	Liu, Zhiyu([email protected])
摘要	The diurnal cycling of the surface mixing/mixed layer (ML) depth, air-sea heat flux, and vertical profiles of the temperature and turbulent kinetic energy dissipation rate in the tropical central South China Sea was observed in summer (June 2017) and winter (January 2018). In the daytime, solar heating warmed and stabilized the ML, and the thickness of the ML can be well characterized by the Zilitinkevich scale as noted in previous studies. By contrast, in the nighttime the ML was deepened by convective turbulence generated by surface cooling. Guided by these observations, we have derived a simple scaling for the nighttime deepening of the ML by simplifying the classic Kraus-Turner type model. We show that the variation of the ML depth can be scaled by a function of the wind speed, air-sea heat flux and the temporal variation of the sea surface temperature, all of which are observable variables at the sea surface. It is found that the scaling works well in reproducing observed variations of the ML depth from hydrographic data. As such, this study advances our understanding of the response of the upper ocean to atmospheric forcing and provides a simple way for predicting the ML depth with solely surface observations. The mixed layer (ML) is the well-mixed region of the upper ocean, which is mainly influenced by air-sea interactions (e.g., wind forcing and buoyancy fluxes). The ML deepening/shoaling processes is critically important for physical, chemical, and biological oceanography. The diurnal variation of the ML depth is caused by daytime heating and nighttime cooling. In the daytime, the surface water gains heat (buoyancy), and then a shallow stable ML (with a thickness of several meters) is formed by the stirring of wind. In the nighttime, by contrast, the surface water loses heat (buoyancy) making the shallow ML unstable, and then the thickness of ML will develop to tens of meters. In this study, we propose a new method to estimate the diurnal variation of the ML depth with wind speed, air-sea heat flux, and sea surface temperature, all of which are observable variables at the sea surface. Our method well characterizes the observed ML depth throughout the diurnal cycle, making it possible to approximate the upper ocean structure without underwater data. Diurnal cycling of stratification and turbulence is ubiquitous in the tropical upper ocean, even in winter A new scaling of the diurnal mixing/mixed layer depth in terms of sea surface variables (wind speed, air-sea heat flux, and sea surface temperature) is proposed and tested It provides a simple way to predict the diurnal mixing/mixed depth with solely surface observations
DOI	10.1029/2024JC021296
收录类别	SCI
语种	英语
资助项目	Natural Science Foundation of Fujian Province[2021J02005]; Natural Science Foundation of Fujian Province of China[2023YFE0126700]; Natural Science Foundation of Fujian Province of China[2022YFA1003804]; National Key R&D Program of China[92258301]; National Natural Science Foundation of China[42006010]; National Natural Science Fundation of China[20720240103]; Fundamental Research Funds for the Central Universities of Xiamen University
WOS研究方向	Oceanography
WOS类目	Oceanography
WOS记录号	WOS:001314617400001
出版者	AMER GEOPHYSICAL UNION
WOS关键词	MIXED-LAYER ; SURFACE ; TURBULENCE ; VARIABILITY
引用统计
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/198571
专题	海洋环流与波动重点实验室
通讯作者	Liu, Zhiyu
作者单位	1.Xiamen Univ, Coll Ocean & Earth Sci, State Key Lab Marine Environm Sci, Xiamen, Peoples R China 2.Xiamen Univ, Coll Ocean & Earth Sci, Dept Phys Oceanog, Xiamen, Peoples R China 3.Chinese Acad Sci, Inst Oceanol, Key Lab Ocean Observat & Forecasting, Qingdao, Peoples R China 4.Chinese Acad Sci, Inst Oceanol, Key Lab Ocean Circulat & Waves, Qingdao, Peoples R China
推荐引用方式 GB/T 7714	Cao, Zhiyong,Liu, Zhiyu,Wang, Dong,et al. Scaling the Diurnal Mixing/Mixed Layer Depth in the Tropical Ocean: A Case Study in the South China Sea[J]. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS,2024,129(9):16.
APA	Cao, Zhiyong,Liu, Zhiyu,Wang, Dong,Wang, Jianing,Lin, Hongyang,&Zhang, Fangtao.(2024).Scaling the Diurnal Mixing/Mixed Layer Depth in the Tropical Ocean: A Case Study in the South China Sea.JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS,129(9),16.
MLA	Cao, Zhiyong,et al."Scaling the Diurnal Mixing/Mixed Layer Depth in the Tropical Ocean: A Case Study in the South China Sea".JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 129.9(2024):16.