An Argo‐Derived Background Diffusivity Parameterization for Improved Ocean Simulations in the Tropical Pacific

Zhu, Yongxuan; Zhang, Ronghua

doi:10.1002/2017gl076269

Cited by 31 publications

(9 citation statements)

References 55 publications

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“…Recent research by Holmes et al (in preparation) has highlighted the global significance of air-sea fluxes and turbulent mixing in this region for modulating ocean heat uptake. However, the parameterization of this vertical mixing in climate models remains a difficult task, and improvements are required in order to reduce model biases (e.g., Sasaki et al 2013;Zhu and Zhang 2018).…”

Section: Enso Modellingmentioning

confidence: 99%

Dynamics and Predictability of El Niño–Southern Oscillation: An Australian Perspective on Progress and Challenges

Santoso

Hendon

Watkins

et al. 2019

Bulletin of the American Meteorological Society

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El Niño and La Niña, the warm and cold phases of El Niño–Southern Oscillation (ENSO), cause significant year-to-year disruptions in global climate, including in the atmosphere, oceans, and cryosphere. Australia is one of the countries where its climate, including droughts and flooding rains, is highly sensitive to the temporal and spatial variations of ENSO. The dramatic impacts of ENSO on the environment, society, health, and economies worldwide make the application of reliable ENSO predictions a powerful way to manage risks and resources. An improved understanding of ENSO dynamics in a changing climate has the potential to lead to more accurate and reliable ENSO predictions by facilitating improved forecast systems. This motivated an Australian national workshop on ENSO dynamics and prediction that was held in Sydney, Australia, in November 2017. This workshop followed the aftermath of the 2015/16 extreme El Niño, which exhibited different characteristics to previous extreme El Niños and whose early evolution since 2014 was challenging to predict. This essay summarizes the collective workshop perspective on recent progress and challenges in understanding ENSO dynamics and predictability and improving forecast systems. While this essay discusses key issues from an Australian perspective, many of the same issues are important for other ENSO-affected countries and for the international ENSO research community.

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Section: Enso Modellingmentioning

confidence: 99%

Dynamics and Predictability of El Niño–Southern Oscillation: An Australian Perspective on Progress and Challenges

Santoso

Hendon

Watkins

et al. 2019

Bulletin of the American Meteorological Society

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“…Since no shear data was available in our field observations, we adopted a fixed value R ω = 7. Actually, on the basis of the historical LADCP and CTD data, Kunze et al (2006) found that the average R ω in the Pacific equals to 7 ± 1 above 2000 m depth, which has been widely assumed in the previous similar studies in the Pacific Ocean (e.g., Li and Xu 2014;Zhu and Zhang 2018).…”

Section: Finescale Parameterizationmentioning

confidence: 74%

Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats

Wang

et al. 2022

J Oceanogr

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The Mindanao Current (MC) bridges the North Pacific low-latitude western boundary current system region and the Indonesian Seas by supplying the North Pacific waters to the Indonesian Throughflow. Although the previous study speculated that the diapycnal mixing along the MC might be strong on the basis of the water mass analysis of the gridded climatologic dataset, the real spatial distribution of diapycnal mixing along the MC has remained to be clarified. We tackle this question here by applying a finescale parameterization to temperature and salinity profiles obtained using two rapid-sampling profiling Argo floats that drifted along the MC. The western boundary (WB) region close to the Mindanao Islands and the Sangihe Strait are the two mixing hotspots along the MC, with energy dissipation rate ε and diapycnal diffusivity Kρ enhanced up to ~ 10–6 W kg−1 and ~ 10–3 m2 s−1, respectively. Except for the above two mixing hotspots, the turbulent mixing along the MC is mostly weak, with ε and Kρ to be 10–11–10–9 W kg−1 and 10–6–10–5 m2 s−1, respectively. Strong mixing in the Sangihe Strait can be basically attributed to the existence of internal tides, whereas strong mixing in the WB region suggests the existence of internal lee waves. We also find that water mass transformation along the MC mainly occurs in the Sangihe Strait where the water masses are subjected to strong turbulent mixing during a long residence time.

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“…Because of the successive arrival of SEs, diapycnal mixing in the subthermocline has significant intreaseasonal variations. Diapycnal mixing has a strong impact on the transformation of interhemispheric water masses in the WBR and hence on the tropical overturning circulation (Fine et al, 1994;Furue and Endoh, 2005;Zhu and Zhang, 2018). The SEs play an important role on the variation of diapycnal mixing in the subthermocline layer.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The diapycnal mixing effects must be parameterized in the ocean climate models. Better understanding of the diapycnal mixing processes is necessary to improve model's parameterizations (Zhu and Zhang, 2018). Since diapycnal mixing remains grossly under-sampled in vast region of the global ocean, the spatial distribution and intensity of diapycnal mixing is an important issue in physical oceanography (Liang et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Diapycnal mixing is of crucial importance to the dynamics and thermodynamics in the WBR (Liu et al, 2017). Biases are substantial in ocean climate models due to insufficient parameterization of background diffusivity in the tropical Pacific Ocean (Zhu and Zhang, 2018). Measurement of turbulent dissipation rate was conducted recently (Liu et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Diapycnal mixing variations induced by subthermocline eddies observed in the north Pacific western boundary region

Nan

Xue²,

Yu³

et al. 2022

Front. Mar. Sci.

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Recent observations prove that subthermocline eddies (SEs) are energetic in the north Pacific western boundary region, where interhemispheric waters meet. Our previous study showed that the SEs play an important role in isopycnal mixing of interhemispheric intermediate waters. Whether the SEs can induce diapycnal mixing in the western boundary region is unknown although it has been found true in the interior region. In this study, based on in-situ observations and fine-scale parameterization method, we show spatial structure and variability of diapycnal mixing induced by the SEs in the north Pacific western boundary region. The SEs are located between 200 and 750 m with a maximum swirl speed reaching 0.5 m s-1 and exhibit significant intra-seasonal variability with the period ranging between 50 and 100 days. Compared with shears induced by tides and near-inertial oscillation, sub-inertial shears induced by the SEs are dominant in the subthermocline layer. Consequently, diapycnal diffusivity is elevated up to O(10-4) m2 s-1 about one order higher than the background value when the SEs were passing by. The integrated diapycnal diffusivity between 200 and 750 m is increased by 210%. Modulated by the SEs, diapycnal mixing in the subthermocline has significant intra-seasonal variations. With more and more SEs being observed around the global oceans, we suggest that SE-induced mixing may not be trivial in closing the global ocean energy budget.

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An Argo‐Derived Background Diffusivity Parameterization for Improved Ocean Simulations in the Tropical Pacific

Cited by 31 publications

References 55 publications

Dynamics and Predictability of El Niño–Southern Oscillation: An Australian Perspective on Progress and Challenges

Dynamics and Predictability of El Niño–Southern Oscillation: An Australian Perspective on Progress and Challenges

Spatial distribution of turbulent diapycnal mixing along the Mindanao current inferred from rapid-sampling Argo floats

Diapycnal mixing variations induced by subthermocline eddies observed in the north Pacific western boundary region

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