Tidal Effect

[susonic]

Hi~ I'm using ROMS2.1 and I've got some problem when I
put tidal effect. My case is North Pacific case(North-west Pacific region) and my cppdefs option is

#define UV_ADV
#define UV_COR
#define UV_VIS2
#undef UV_VIS4
#define TS_DIF2
#undef TS_DIF4
#define MIX_GEO_TS
#undef MIX_GEO_UV
#define MIX_S_UV
#define MIX_S_TS
#define DJ_GRADPS
#undef FLOATS
#undef ANA_PSOURCE
#define UV_PSOURCE
#define TS_PSOURCE
#define SSH_TIDES
#define ADD_FSOBC
#define ADD_M2OBC
#define UV_TIDES
#define TS_U3HADVECTION
#define TS_C4VADVECTION
#undef ANA_INITIAL
#undef ANA_SMFLUX
#undef ANA_STFLUX
#undef ANA_SSFLUX
#define NONLIN_EOS
#define SALINITY
#define SOLVE3D
#define MASKING
#define SPLINES
#define QCORRECTION
#define SCORRECTION
#define SOLAR_SOURCE
#define CURVGRID
#define AVERAGES
#undef AVERAGES_AKV
#undef AVERAGES_AKT
#undef AVERAGES_AKS
#undef EASTERN_WALL
#undef SOUTHERN_WALL
#undef NORTHERN_WALL
#define WESTERN_WALL
#define LMD_MIXING
#ifdef LMD_MIXING
#define LMD_RIMIX
#define LMD_CONVEC
#define LMD_SKPP
#define LMD_BKPP
#define LMD_NONLOCAL
#endif
#define TCLIMATOLOGY
#define ZCLIMATOLOGY
#define M2CLIMATOLOGY
#define M3CLIMATOLOGY
#define TCLM_NUDGING
#define ZCLM_NUDGING
#define M2CLM_NUDGING
#define M3CLM_NUDGING
#define ANA_BSFLUX
#define ANA_BTFLUX
#define EAST_M2FLATHER
#undef EAST_M2NUDGING
#define EAST_M3RADIATION
#define EAST_M3NUDGING
#define EAST_FSCHAPMAN
#define EAST_TRADIATION
#define EAST_TNUDGING
#undef EAST_VOLCONS
#define SOUTH_M2FLATHER
#undef SOUTH_M2NUDGING
#define SOUTH_M3RADIATION
#define SOUTH_M3NUDGING
#define SOUTH_FSCHAPMAN
#define SOUTH_TRADIATION
#define SOUTH_TNUDGING
#undef SOUTH_VOLCONS
#define NORTH_M2FLATHER
#define NORTH_M3RADIATION
#define NORTH_M3NUDGING
#define NORTH_FSCHAPMAN
#define NORTH_TRADIATION
#define NORTH_TNUDGING
#undef NORTH_VOLCONS
#undef WEST_M2FLATHER
#undef WEST_M2NUDGING
#undef WEST_M3RADIATION
#undef WEST_M3NUDGING
#undef WEST_FSCHAPMAN
#undef WEST_TRADIATION
#undef WEST_TNUDGING
#undef WEST_VOLCONS

The problem is when I add tide with 'M2 S2 N2 K2 K1 O1 P1 Q1 Mf Mm'
the model always blows up except when I add only 'M2 S2'. I want to put more than 'M2 S2' but it doesn't work! Anyone knows what I'm missing?
I use 'TPXO6.nc'.
Thanks in advance.

[kate]

I can successfully add the 8 diurnal and semidiurnal constituents. I do need a short timestep, however. Does yours blow up during the timestepping? Have you tried smaller timesteps? Have you tried *much* smaller timesteps?

[susonic]

Yes, It stopped while calculating a time step.Thanks Kate~ And I'll try

to reduce the time step~

By the way, I am just wondering why should I change the time step?

Is the time step change concerned with blow up ?

I think the time step is just the time step.

I don't understand....

Would you mind explaining the reason?

Thanks in advance and Have a good day~

[kate]

There will be a timestep beyond which the model will be unstable. This stability boundary depends on many things, including numerical scheme used, grid spacing, and maximum velocity. Adding tides increases the maximum velocity and you could therefore need a shorter timestep. Also, adding barotropic tides could lead to the need for a shorter baroclinic step to resolve things like bottom stress.

[susonic]

What a detail answer! Thanks for a Gooooooood explanation.

I'll apply the shorter time step and let you know how it goes.

Thanks again! And have a GOOD day~