[MITgcm-support] Non-Hydrostatic Energy Budget

[Bertrand Delorme]

Hi everyone,

Follow-up to my previous post below. It seems that the diagnostics Wm_Advec, Wm_Diss and AB_gW are available with the code in NH mode. However, to have a complete budget, I would need the total vertical pressure gradient (something like a Wm_dPhiZ diagnostic). It would also be nice to have the tendency of the vertical velocity (something like TOTWTEND). I can’t find any of these two diagnostics in the code of the model. Is there a reason why those haven’t been included with the other diagnostics of the vertical momentum equation? Is there any ways to access them outside of an offline calculation?

Thank you,

Bertrand

De : Bertrand DELORME <bdelorme at stanford.edu>
Date : vendredi 13 novembre 2020 à 16:24
À : "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
Objet : Non-Hydrostatic Momentum Budget

Hi everyone,

I am trying to compute the fully non-hydrostatic energy budget of my internal wave simulation using the Diagnostics package and I have a few questions:


i)                    I read that the diagnostics Um_Advec and Vm_Advec already contain the Coriolis terms. Does that mean that in NH mode, Um_Advec contains both the -f*v and +fh*w, where f is the vertical component of the Coriolis parameter and fh the horizontal component of the Coriolis parameter? When calculating the energy budget, one needs to take the dot product of the momentum equations with the velocity vector, effectively canceling out the Coriolis terms in the energy equation. However, using only the horizontal momentum equations diagnostics (i.e.,  Um_Advec and Vm_Advec), we don’t get the -fh*u term coming from the vertical momentum equation that permits to cancel out the +fh*w term from the zonal momentum equation. Is that really what is happening when we perform U . Um_Advec + V . Vm_Advec (i.e., we get a u*fh*w term that is not balanced)? If yes, is there a way to get a Wm_Advec term from the diagnostics package or do I have to calculate it offline when performing my energy budget?


ii)                   In a previous post from Jean-Michel, I read that the surface pressure horizontal gradient needs to be added to the Um_dPHdx and Vm_dPHdy diagnostics. However, when I run my simulation, I don’t get the Um_dPHdx and Vm_dPHdy diagnostics but I get the Um_dPhiX and Vm_dPhiY diagnostics instead, which seem to already incorporate the surface pressure gradient. Am I right on that? Also, do these new diagnostics incorporate the NH pressure field?

Thank you,

Bertrand Delorme
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