[MITgcm-support] How to calculate the internal tide disspation from MITgcm output ?

[Mike Fan]

Hello, everyone

Recently I try to get the disspation of internal tide from MITgcm output, I have set the coefficients for constant viscosity, diffusion, and bottom friction. I want to know that, in this way, can I use the equations(15-18) of You et al. (2023) to do the job?

[cid:11fddd70-bb73-4fc8-a7ac-eade39c97c0c]
[cid:9631aa7a-893b-4d27-8daa-788aa288b2cc]

In my experience (in the only M2 internal tide model), the uncertainty of dissipation caused by diffusion (Equ.17) is the greatest. When the density perturbation (rho') is calculated by rho-mean(rho), this term (sum of Equ.(16-18) ~20GW) is absolutely dominant and is obviously larger than that estimated by Equ.8 (rhs ~6GW). When the density perturbation (rho') is calculated by harmonic analysis, the result (sum of Equ.(16-18) ~3GW) is smaller than that estimated by Equ.8. I'm not sure that if the choice of parameterization scheme may lead to differences in the calculation of dissipation, so I would like to ask, in a model with only M2 internal tide, how can I use the given constant parameters (viscosity, diffusion and bottom friction) to directly obtain the disspation generated by the internal tide?

Here is my "data" file setting:
# ====================
# | Model parameters |
# ====================
#
# Continuous equation parameters
 &PARM01
 TrefFile='Tannualref',
 sRef= 50*34.5,
 viscAh=5.0,
 viscAz=1.5E-4,
 diffKhT=5.0,
 diffKhS=5.0,
 diffKzT=1.5E-5,
 diffKzS=1.5E-5,
 no_slip_sides=.FALSE.,
 no_slip_bottom=.TRUE.,
 bottomDragQuadratic=2.5E-3,
 eosType='LINEAR',
 staggerTimeStep=.TRUE.,
 tAlpha=2.E-4,
 sBeta =0E-4,
 gravity=9.81,
 implicitFreeSurface=.TRUE.,
 exactConserv=.TRUE.
 nonHydrostatic=.FALSE.,
 useCoriolis=.TRUE.,
 hFacMin=0.2,
 hFacInf=0.2,
 hFacSup=1.8,
 tempStepping=.TRUE.,
 saltStepping=.FALSE.,
#- not safe to use globalFiles in multi-processors runs
#globalFiles=.TRUE.,
 readBinaryPrec=64,
 writeBinaryPrec=32,
 writeStatePrec=32,
 useSingleCpuIO=.TRUE.,
 &


Any reply or suggestion will be greatly appreciated.

-Mike
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