[MITgcm-support] Non-Hydrostatic Momentum Budget

[Bertrand Delorme]

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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