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

[Jody Klymak]

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This is probably outdated, but the writeup and the diagnostic may help you with your problem: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>
Reply-To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
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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