Hello everyone,
I have a confusion about TIDE_START, I am going to develop my case followling 'create_sandy_application.m'. In ocean_sandy.in file, some time parameters setting are :
DSTART = 56228.5d0 56228.5d0 ! days
TIDE_START = 52866.0d0 ! days
TIME_REF = 18581117.0d0 ! yyyymmdd.dd
Sandy case is simulated from 27-Oct-2012 to 2-Nov-2012, So I know DSTART = Time_start(27-Oct-2012)- TIME_REF(18581117.0d0), And all the forcing files started at 56228 days. I want to know what the meaning of TIDE_START, and I usually use the TPXO2ROMS_v4pt0_script.m to create tide forcing file, if the 't0' in the script is accosiated TIDE_START ? and how to calculate the TIDE_START?
A confusion about TIDE_START (COAWST_SANDY CASE)
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Rocky_Wang
- Posts: 50
- Joined: Tue Mar 01, 2016 1:38 am
- Location: the Ocean University of China
A confusion about TIDE_START (COAWST_SANDY CASE)
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Re: A confusion about TIDE_START (COAWST_SANDY CASE)
The idea is that TIDE_START is the tidal offset from your TIME_REF. If your tidal t0 and your DSTART match, then you have it about right (plus or minus half a day).
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johnluick
Re: A confusion about TIDE_START (COAWST_SANDY CASE)
Hi Rocky,
You have:
DSTART = 56228.5d0 56228.5d0 ! days
TIDE_START = 52866.0d0 ! days
TIME_REF = 18581117.0d0 ! yyyymmdd.dd
1. Why do you have two values of DSTART?
2. Did you mean to have DSTART=TIDE_START? Just checking, because the digits are similar but not the same.
3. You seem to have three different times (DSTART, TIDE_START, and t0 are all different, even if you add your TIME_REF to DSTART and TIDE_START).
4. t0 in TPXO2ROMS specifies time at which the tidal phase lags (aka "little g's") are computed.
5. I haven't used a TIME_REF other than -2 for years, and I usually set DSTART=TIDE_START. I set t0 the same time (but it is in Matlab datenumber).
6. Look at this section from set_tides.f90. This is where the phase is set. Run your model for one time step, printing out cff and any other variables you want to know (put a print statement in the .F file.) If t0 corresponds to the starting time step of the model, you should be right.
!-----------------------------------------------------------------------
! Add tidal elevation (m) to sea surface height climatology.
!-----------------------------------------------------------------------
!
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))
Etide(i,j)=Etide(i,j)*rmask(i,j)
END DO
END DO
END IF
END DO
7. I'm surprised that Kate says "If your tidal t0 and your DSTART match..." because I thought DSTART was used only as a time stamp for stdout (i.e., not used internally for any phase calculation or anything), but then she knows way more than I ever will about ROMS.
You have:
DSTART = 56228.5d0 56228.5d0 ! days
TIDE_START = 52866.0d0 ! days
TIME_REF = 18581117.0d0 ! yyyymmdd.dd
1. Why do you have two values of DSTART?
2. Did you mean to have DSTART=TIDE_START? Just checking, because the digits are similar but not the same.
3. You seem to have three different times (DSTART, TIDE_START, and t0 are all different, even if you add your TIME_REF to DSTART and TIDE_START).
4. t0 in TPXO2ROMS specifies time at which the tidal phase lags (aka "little g's") are computed.
5. I haven't used a TIME_REF other than -2 for years, and I usually set DSTART=TIDE_START. I set t0 the same time (but it is in Matlab datenumber).
6. Look at this section from set_tides.f90. This is where the phase is set. Run your model for one time step, printing out cff and any other variables you want to know (put a print statement in the .F file.) If t0 corresponds to the starting time step of the model, you should be right.
!-----------------------------------------------------------------------
! Add tidal elevation (m) to sea surface height climatology.
!-----------------------------------------------------------------------
!
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))
Etide(i,j)=Etide(i,j)*rmask(i,j)
END DO
END DO
END IF
END DO
7. I'm surprised that Kate says "If your tidal t0 and your DSTART match..." because I thought DSTART was used only as a time stamp for stdout (i.e., not used internally for any phase calculation or anything), but then she knows way more than I ever will about ROMS.