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Ticket Comment Diff – NEMO

Changes between Initial Version and Version 1 of Ticket #1723, comment 5


Ignore:
Timestamp:
2019-10-02T11:17:05+02:00 (5 years ago)
Author:
Robin_Waldman
Comment:

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  • Ticket #1723, comment 5

    initial v1  
    22 
    33Contrary to the modification proposed in Ticket #1584, the updates proposed by Julien J. do not only fix the momentum/KE trend diagnostic but also modify the physics of NEMO model. Specifically: 
    4 - Not updating the barotropic trend from the time splitting estimate (the variable ua_b), either in dynzdf_imp or in dyn_nxt is problematic for the time stepping of the barotropic velocities. Indeed, the barotropic trend contains all dynamical forcings of vertical mean velocities: the vertical mean Coriolis, advection, lateral dissipation, pressure force, bottom and surface friction. So that removing the barotropic trend update is equivalent to neglecting all those forcings but the bottom and surface friction which have been added to dyn_zdf_imp in Julien J.'s fix. A solution for this issue is to uncomment lines 395 to 404 of dynzdf_imp.F90 provided by Julien J. (in attachment). 
     4- Not updating the barotropic trend from the time splitting estimate (the variable ua_b), either in dyn_zdf_imp or in dyn_nxt is problematic for the time stepping of the barotropic velocities. Indeed, the barotropic trend contains all dynamical forcings of vertical mean velocities: the vertical mean Coriolis, advection, lateral dissipation, pressure force, bottom and surface friction. So that removing the barotropic trend update is equivalent to neglecting all those forcings but the bottom and surface friction which have been added to dyn_zdf_imp in Julien J.'s fix. A solution for this issue is to uncomment lines 395 to 404 of dynzdf_imp.F90 provided by Julien J. (in attachment). 
    55- Accounting for surface and bottom friction within the baroclinic time step, in dynzdf_imp.F90 as proposed by Julien J., is not equivalent to including it to the barotropic trend, as it is done normally in dynspg_ts.F90 under time splitting. In particular, bottom and surface friction are a forcing of the barotropic dynamics, so it is preferrable to include them within dynspg_ts.F90 to ensure numerical stability. 
    66