tidal model problem

[duckweed]

Hi,
I have some problem about the tidal model:
1) in set_tides.F :

Code: Select all

      
Etide(:,:)=0.0_r8
      cff=2.0_r8*pi*(time(ng)-tide_start*day2sec)
      DO itide=1,NTC
        IF (Tperiod(itide).gt.0.0_r8) THEN
          omega=cff/Tperiod(itide)
          DO j=JstrR,JendR
            DO i=IstrR,IendR
              Etide(i,j)=Etide(i,j)+                                    &
     &                   ramp*SSH_Tamp(i,j,itide)*                      &
     &                   COS(omega-SSH_Tphase(i,j,itide))
#  ifdef MASKING
              Etide(i,j)=Etide(i,j)*rmask(i,j)
#  endif
            END DO
          END DO
        END IF
      END DO

It does not take into account nodal factor 'f' and revised angle 'u'. If take into accout the Etide:
Etide(i,j)=Etide(i,j)+ f(itide)*ramp*SSH_Tamp(i,j,itide)* COS(omega+u(itide)-SSH_Tphase(i,j,itide))
And the Etide(:,:)=0.0_r8, need to modify to Mean tide level?

2)
How about OSU Tidal Data in southeast China coastal waters ?

This is my cpp about tide and boundary:

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/* boundary conditions*/
#define NORTHERN_WALL
#undef EW_PERIODIC

#undef ANA_M2OBC
#undef ANA_FSOBC

#define SOUTH_M3RADIATION
#define SOUTH_TGRADIENT
#define EAST_M3RADIATION
#define EAST_TGRADIENT
#define WEST_M3RADIATION
#define WEST_TGRADIENT

/* define UV_TIDES to specify boundary tidal currents from data e.g. ADCIRC */
/* define UV_TIDES to compute tidal currents using reduced physics */
#define SSH_TIDES       /* read tidal SSH     from file */
#define SOUTH_FSCHAPMAN
#define EAST_FSCHAPMAN
#define WEST_FSCHAPMAN

#define UV_TIDES        /* read tidal U and V from file */
#define RAMP_TIDES	/* ramping (over one day) tidal forcing */ 

#define SOUTH_M2FLATHER
#define WEST_M2FLATHER
#define EAST_M2FLATHER

The following two figures are my study area and result.The red area is model area.
Why such a big gap between simulation and observation?
My tidal data come from OTPS. It has 10 tide: M2,S2,N2,K2,O1,K1,P1,Q1,M4,MS4. The boundary data from the 10 tides.
Thank you !

[BAN]

Hi
Regarding nodal factor etc. it is as remember it accounted for in preprocessing, and is therefore not needed within the model. See https://www.myroms.org/wiki/index.php/Tidal_Forcing and the check out the code on http://marine.rutgers.edu/~hunter/roms/tides/otps/

You seem to run in 2D
Here are some options which have worked for me.

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/* Momentum terms.................................................. */
/*default horizontal adv. 2D-momentum is 4th-order centered */
#define UV_COR   /* Compute Coriolis term */
#define UV_QDRAG /* Quadratic bottm friction */
#define UV_VIS2  /* Comp. horiz. Laplacian viscosity */

/* General model terms.................................................. */
/* by default only 2D-physics are used (3D-physics if 'define SOLVE3D') */
#define MASKING  /* There is land in the domain to be masked out   */

/* Open boundary condition settings..................................... */
#define WEST_FSCHAPMAN  /* Western Chapman condition on free sueface */
#define WEST_M2FLATHER  /* Western Flather condition on 2D momentum */
#define EAST_FSCHAPMAN  /* See above */
#define EAST_M2FLATHER  /* See above */
#define SOUTH_FSCHAPMAN /* See above */
#define SOUTH_M2FLATHER /* See above */
#define NORTH_FSCHAPMAN /* See above */
#define NORTH_M2FLATHER /* See above */

/* Analytical fields ................................................. */
#define ANA_SMFLUX /* Ana. kinem. surface mom. stress, by default=0 */
#define ANA_FSOBC  /* Ana. free-surface boundary conditions */
#define ANA_M2OBC  /* Ana. 2D momentum boundary conditions */
#define ANA_INITIAL  /* Ana. initial conditions  */

/* Tide options ................................................. */
#define SSH_TIDES  /* Imposing tidal elevation */
#define RAMP_TIDES /* tides are ramped 1 day from zero */
#define FSOBC_REDUCED  /* boundary pg is calculated using bounday zeta */

As you can see I use reduced physics at the border in this run to generate currents, but your option define UV_TIDES also worked for me.

Regarding the Observation vs. Model results they seem to be of the same period and amplitude. It seems as if the Observation is not referring to mean surface level and that there is a shift in time. This is most likely related to the first problem, have a look at the links.