[MITgcm-support] 回复: Question about internal tide energy flux balance

Sun Aug 10 18:07:44 EDT 2025

Hi Sean,

Below are two links to old notes of mine about Jody's energy diagnostics code. They were only intended to be notes to myself (and they're 8 years old), so they might be a bit terse, but I think they could help answer some of your questions.

The first link is about intermediate calculations within the fortran code. The second link is about an idealized setup that looks at the magnitudes and behaviors of the various terms.

https://drive.google.com/file/d/1ixlnFmhKCy0EGrHQ7vKlldwOm_mOGVIa/view?usp=sharing

https://drive.google.com/file/d/1lT56CS_Fgw_g9ecvrxtv_Tt9LNeb3QlS/view?usp=sharing

Ken Hughes
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From: MITgcm-support <mitgcm-support-bounces at mitgcm.org> on behalf of Shiqiang Hu (ENV - Postgraduate Researcher) <Shiqiang.Hu at uea.ac.uk>
Sent: Sunday, August 10, 2025 1:49 PM
To: mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
Subject: [MITgcm-support] 回复: Question about internal tide energy flux balance

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Hi Jody,

I have been reading your reference materials which is useful. Finally I was able to output the energy dignostics in latest version based on your code,  but several questions have arisen:

1, For baroclinic energy equation  [cid:592a7939-f6bc-48b9-b311-cb17b6089067]  how did you calculate the first three terms from dignostics outputs, while it seems the equation used in dignostics code is the total energy equation? I can only find your github pages cause the link in your paper seems no longer valid. I'm confused that Fbc should be <u'p'>, but the dignostics code use the original velosity uVel and vVel directly to get uPbc and so on.

2, For Conversion term, the W is derived from [cid:791c1654-63b9-4bb1-9f91-ec3c854ef76b] in Kang's 2011 paper. So we don't need the W velosity from the model output? I'm not sure if they are different or my code was wrong.

Sorry if it’s a lot to explain, but I could really use your help with this.

Thanks and cheers!
Sean
University of East Anglia

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发件人: MITgcm-support <mitgcm-support-bounces at mitgcm.org> 代表 Jody Klymak <jklymak at uvic.ca>
发送时间: 2025年7月19日 1:18
收件人: mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
主题: Re: [MITgcm-support] Question about internal tide energy flux balance

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Hi Sean

This is probably outdated, but the writeup and the diagnostic may help you with your problem:

https://ocean-physics.seos.uvic.ca/~jklymak/MITgcm/

in particular  https://ocean-physics.seos.uvic.ca/~jklymak/MITgcm/energy_diagnostics_fill.F

and

https://ocean-physics.seos.uvic.ca/~jklymak/MITgcm/EnergyDiagnostic.pdf

This was used extensively in 10.1175/2010JPO4396.1<https://doi.org/10.1175/2010JPO4396.1> and 10.1175/JPO-D-16-0061.1

Hopefully that helps, if not, I can probably provide more guidance.

Cheers Jody

From: MITgcm-support <mitgcm-support-bounces at mitgcm.org> on behalf of "Shiqiang Hu (ENV - Postgraduate Researcher)" <Shiqiang.Hu at uea.ac.uk>
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Date: Friday, July 18, 2025 at 9:58 AM
To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Subject: [MITgcm-support] Question about internal tide energy flux balance

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Hi MITgcm commuity,

Hope you all well.

I built an idealized 3D internal tide model based on internal_wave experiment<https://github.com/MITgcm/MITgcm/blob/master/verification/internal_wave> to calculate the energy flux F=<u'p'>(Nash et al., 2005<https://doi.org/10.1175/JTECH1784.1>). Periodic 1-mode internal tides propagate to the right and interact with a simple topography. The model works but I got stuck at the energy flux balance part. Sometimes when I chose a small area within the topography to calculate the net energy flux across its boundary, the result is positive, which means there are rather dissipation but genaration of enerny. So I wanna ask if someone has experience with this.

Basically, I use RHOAnoma+rhoConst to get original density rho, cause the paper gets density anomaly from rho(z,t)-rho_mean(z), where rho_mean(z) is the time mean vertical density profile (I guess I could also just use the Rhoref(z) as the reference profile?). The question is the C-grids, should I calculate these values on T-points or U-V points so the energy could be more balenced? Or maybe some other factors I didn't realize?

By the way, the non-hydrostatic pressure is quite small, so I ignored it.

Thanks for any suggestions.

Kind regards,

Sean

University of East Anglia
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