Scaling wind stirring effects in an oceanic bulk mixed layer model with application to an OGCM of the tropical Pacific

Zhu, Yongxuan

doi:10.1007/s00382-017-3990-5

Cited by 11 publications

(10 citation statements)

References 64 publications

(77 reference statements)

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“…Solar radiation penetrating out of the bottom of the ML ( Q pen ) is written as Q pen ( Chl , H m ), which is determined by Chl and the ML depth ( H m ). H m is predicted using a bulk ML model in the HCM (Chen et al, ; Zhu & Zhang, ). Correspondingly, the impact of Chl TIW on Q pen (

Q_{pen - {Chl}_{TIW}}

) can be approximately estimated as follows:

Q_{pen - {Chl}_{TIW}} = Q_{pen} ((),, Chl, H_{m}) - Q_{pen} ((),, \overset{true¯}{italicChl}, H_{m})

…”

Section: Methodsmentioning

confidence: 99%

A Positive Feedback Onto ENSO Due to Tropical Instability Wave (TIW)‐Induced Chlorophyll Effects in the Pacific

Tian

Wang

2019

Geophysical Research Letters

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Tropical instability waves (TIWs) induce large physical and biological perturbations, which have a feedback onto the tropical Pacific climate and ecosystem. However, the extent to which TIW‐induced chlorophyll perturbations (ChlTIW) can influence El Niño–Southern Oscillation (ENSO) remains unknown. Here we used a hybrid‐coupled model to investigate the ChlTIW effect on ENSO. Two experiments are conducted, one with the ChlTIW effect being represented in the control run (CTRL) and other with the ChlTIW effect being purposely excluded by filtering out ChlTIW signals (FILT). Results show that the amplitude of ENSO is increased by 27% in CTRL compared to FILT. ChlTIW tends to modulate the penetrative solar radiation in the upper ocean, acting to weaken the intensity of TIWs. Then, the weakened TIWs lead to a reduction in the equatorward meridional heat transport and consequently less warming effect on the cold tongue. Therefore, La Niña conditions tend to be intensified, and ENSO amplitude is increased.

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Q_{pen - {Chl}_{TIW}}

) can be approximately estimated as follows:

Q_{pen - {Chl}_{TIW}} = Q_{pen} ((),, Chl, H_{m}) - Q_{pen} ((),, \overset{true¯}{italicChl}, H_{m})

…”

Section: Methodsmentioning

confidence: 99%

A Positive Feedback Onto ENSO Due to Tropical Instability Wave (TIW)‐Induced Chlorophyll Effects in the Pacific

Tian

Wang

2019

Geophysical Research Letters

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“…In ocean general circulation models (OGCMs), mixing parameterization schemes such as the Mellor–Yamada (MY) scheme 5 and the K-profile parameterization (KPP) scheme 6 are adopted to represent entrainment. Because the parameterization of the entrainment buoyancy flux at the ML base ( ) is key to developing the mixing parameterization, the flux has been investigated in several studies 7 – 10 . Studies of the atmospheric boundary layer (ABL) 11 – 14 are also useful because the entrainment process in the ocean surface boundary layer is dynamically similar to that in the ABL.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, m in Eq. ( 2 ) should depend on the Rossby number 10 , 22 . However, the dependence of m on has not been well investigated.…”

Section: Introductionmentioning

confidence: 99%

Nonlinearly interacting entrainment due to shear and convection in the surface ocean

Ushijima

Yoshikawa

2022

Sci Rep

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Large-eddy simulations were performed to investigate the entrainment buoyancy flux at the mixed layer base due to nonlinearly interacting shear-driven turbulence (ST) and convective turbulence (CT). The fluxes due to pure ST and pure CT were first evaluated, and their scalings were derived. The entrainment flux due to coexisting ST and CT was then evaluated and compared to the scaling-based fluxes due to the pure turbulences. It was found that nonlinear effects reduce the entrainment flux by $$30 \%$$ 30 % when the turbulent kinetic energy production rates of ST and CT are comparable. The mixing parameterization schemes used in ocean general circulation models (OGCMs) fail to accurately reproduce the mixing due to the pure turbulences and/or the nonlinear effects, and thus the mixed layer depth (MLD). Because analysis using global datasets suggests that nonlinear effects are large at the mid-latitudes, these results indicate that the nonlinear effects might be responsible for the deep MLD biases in OGCMs and that mixing parameterization schemes need to be improved to correctly represent ocean surface mixing due to shear and convection, as well as waves, in OGCMs.

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“…Errors in vertical mixing schemes inevitably misrepresent the vertical redistribution of momentum, heat, and so on. Some previous studies have discussed the relationship between uncertainties in vertical mixing schemes and tropical biases (Zhang and Zebiak 2002;Hazeleger and Haarsma 2005;Harrison and Hallberg 2008;Jochum 2009;Moum et al 2013;Sasaki et al 2013;Zhu andZhang 2018a,b, 2019). But the relationship between the subtropical cold bias and the errors in vertical mixing schemes has been rarely examined although some hints are seen in some previous studies.…”

Section: Introductionmentioning

confidence: 99%

North Pacific Upper-Ocean Cold Temperature Biases in CMIP6 Simulations and the Role of Regional Vertical Mixing

2020

Self Cite

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Substantial model biases are still prominent even in the latest CMIP6 simulations; attributing their causes is defined as one of the three main scientific questions addressed in CMIP6. In this paper, cold temperature biases in the North Pacific subtropics are investigated using simulations from the newly released CMIP6 models, together with other related modeling products. In addition, ocean-only sensitivity experiments are performed to characterize the biases, with a focus on the role of oceanic vertical mixing schemes. Based on the Argo-derived diffusivity, idealized vertical diffusivity fields are designed to mimic the seasonality of vertical mixing in this region, and are employed in ocean-only simulations to test the sensitivity of this cold bias to oceanic vertical mixing. It is demonstrated that the cold temperature biases can be reduced when the mixing strength is enhanced within and beneath the surface boundary layer. Besides, the temperature simulations are rather sensitive to the parameterization of static instability, and the cold biases can be reduced when the vertical diffusivity for convection is increased. These indicate that the cold temperature biases in the North Pacific can be largely attributed to biases in oceanic vertical mixing within ocean-only simulations, which likely contributes to the even larger biases seen in coupled simulations. This study therefore highlights the need for improved oceanic vertical mixing in order to reduce these persistent cold temperature biases seen across several CMIP models.

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Scaling wind stirring effects in an oceanic bulk mixed layer model with application to an OGCM of the tropical Pacific

Abstract: the constant m 0 case. As the related cooling effect from the upwelling is enhanced, the simulated SST is slightly cooled down in the eastern equatorial Pacific. Further applications and implications are also discussed.

Cited by 11 publications

References 64 publications

A Positive Feedback Onto ENSO Due to Tropical Instability Wave (TIW)‐Induced Chlorophyll Effects in the Pacific

A Positive Feedback Onto ENSO Due to Tropical Instability Wave (TIW)‐Induced Chlorophyll Effects in the Pacific

Nonlinearly interacting entrainment due to shear and convection in the surface ocean

North Pacific Upper-Ocean Cold Temperature Biases in CMIP6 Simulations and the Role of Regional Vertical Mixing

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