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Cited by 27Oceanographic and Atmospheric ProcessesFluid Dynamics and Turbulent FlowsMeteorological Phenomena and Simulations

Variations of Equatorial Shear, Stratification, and Turbulence Within a Tropical Instability Wave Cycle

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Inoue, Ryuichiro, Lien, Ren‐Chieh, Moum, James N., Perez, Renellys C., Gregg, Michael C.·2019·Journal of Geophysical Research: Oceans
DOI 10.1029/2018jc014480
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Abstract

Abstract Equatorial Internal Wave Experiment observations at 0°, 140°W from October 2008 to February 2009 captured modulations of shear, stratification, and turbulence above the Equatorial Undercurrent by a series of tropical instability waves (TIWs). Analyzing these observations in terms of a four‐phase TIW cycle, we found that shear and stratification within the deep‐cycle layer being weakest in the middle of the N‐S phase (transition from northward to southward flow) and strongest in the late S phase (southward flow) and the early S‐N phase (transition from southward to northward flow). Turbulence was modulated but showed less dependence on the TIW cycle. The vertical diffusivity (KT) was largest during the N (northward flow) and N‐S phases, when stratification was weak, despite weak shear, and was smallest from the late S phase to the S‐N phase, when stratification was strong, despite strong shear. This tendency was less clear in turbulent heat flux because vertical temperature gradients were small at times when KT was large, and large when KT was small. We investigated the dynamics of shear and stratification variations within the TIW cycle by using an ocean general circulation model forced with observed winds. The model successfully reproduced the observed strong shear and stratification in the S phase, except for a small phase difference. The strong shear is explained by vortex stretching by TIWs. The strong stratification is explained by meridional and vertical advection.

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  • The influence of TIW-induced mixing on long term means is less than expected from the measurements made in 2008.

    “This suggests that the influence of TIW-induced mixing on long term means is less than expected from the measurements made in 2008 (Moum et al., 2009;Inoue et al., 2012Inoue et al., , 2019)).”

    From Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues (2022) · cites this paper as Inoue et al., 2019

    Section 6 (Summary; page unavailable) says the largest diffusivity and heat flux occurred during an anomalous fourth TIW, while Section 5.1 says the dependence of diffusivity and heat flux on TIW phase was less clear across the observed waves. These findings support caution about extrapolating from the intense 2008 event, but the paper does not assess TIW-induced mixing's influence on long-term means or compare it with expectations from those measurements. (LLM, conf=0.79)

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Cited by

Sorted by citations

Authors
Inoue, R., Lien, R., Moum, J. N., Perez, R. C., & Gregg, M. C.
Affiliations
  • Japan Agency for Marine-Earth Science and Technology (JP)
  • University of Washington (US)
  • Oregon State University (US)
  • National Oceanic and Atmospheric Administration (US)
Corresponding author
Inoue, Ryuichiro
ORCID
Venue
Journal of Geophysical Research: Oceans
Publisher
American Geophysical Union (AGU)
Published
2019-03
Volume
124
Issue
3
Pages
1858-1875
ISSN
  • 2169-9275 (ISSN-L)
  • 2169-9291
DOI
10.1029/2018jc014480
OpenAlex
W2916098479
Cited by
27
References
0
Citations by year
2026: 2 · 2025: 3 · 2024: 5 · 2023: 2 · 2022: 6 · 2021: 5 · 2020: 3 · 2019: 1
FWCI
2.07
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Geophysical Research Oceans (publishedVersion)
  • NOAA Institutional Repository (submittedVersion)
Funders
Division of Ocean Sciences (0424133, 0726523, 0728375)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
  • Physical Sciences › Engineering › Computational Mechanics › Fluid Dynamics and Turbulent Flows
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Meteorological Phenomena and Simulations
Keywords
tropical instability waves, ocean stratification, turbulent flow, vertical diffusivity, Equatorial Undercurrent, vortex stretching, turbulent heat flux, ocean general circulation model

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