Restarts at t = 0h

[tomgowan]

Is there a way to generate restart files at t =0h (i.e., immediately after model initialization)? I've tried setting restart_interval = 0,-1 and restart_interval = 24,-1` with no success. Thanks.

[pjpegion]

Someone else might know more specifics, but it is my understanding that the code to write the restarts is at the end of the time-loop, so the best you can do is run the model one time-step and write out the restarts. I just checked the model code, and nhours_fcst can be a fraction of an hour (e.g 0.25 if you are running with a 900 second time-step)

[tomgowan]

Thanks @pjpegion . We have been able to do this in MPAS and WRF (WRF required some source code changes). I'm currently testing if something can be added to FV3/module_fcst_grid_comp.F90 that will force UFS to generate these restarts at t-0h. If you are correct that the first check to generate restarts is at the end of the first time-loop, this may not be doable.

[jiandewang]

for MOM, this is what you need in MOM_input
SAVE_INITIAL_CONDS = True ! [Boolean] default = False
! If true, write the initial conditions to a file given by IC_OUTPUT_FILE.
I think CICE will save IC inside history directory

[tomgowan]

Thanks @jiandewang. I should have been more specific in that I'm trying to do this in UFS/FV3. It doesn't look like this option exists there. Also, would this option generate restart files or just standard output files?

[jiandewang]

Thanks @jiandewang. I should have been more specific in that I'm trying to do this in UFS/FV3. It doesn't look like this option exists there. Also, would this option generate restart files or just standard output files?

for MOM it will simply generate IC, not restart file

[tomgowan]

I was able to generate restarts by editing the source code file FV3/module_fcst_grid_comp.F90. I first simply forced FV3 to generate restarts files every time step within the fcst_run_phase_2 subroutine by removing the if statements that checked if restarts should be generated based on the restart_interval parameter in model_configure. As @pjpegion correctly assumed, this resulted in the first set of restart files being generated after the first time step.

I then decided to move this code into the preceding subroutine named fcst_run_phase_1 (before any integration occurs). Somewhat surprisingly, this worked and restart files were generated at t=0. There do not appear to be any issues with the files and I was able to restart a run using them.

Here's my final implementation within fcst_run_phase_1:
*note that a few variables shown here need to be added to the subroutine

737 !-------------------------------------------------------------------------
738 !********************** START MY CHANGES *****************************
739 !-------------------------------------------------------------------------
740 
741 ! This code block was added to generate restart files at t=0 (just after
742 ! intialization). The default location to generate restart files is in the
743 ! subroutine below called "fcst_run_phase_2". However, this subroutine is
744 ! first called after the first model time step, and thus, will not allow
745 ! for restart files to be generated at t=0. Copying the calls to generate 
746 ! restarts here, in the subroutine called "fcst_run_phase_1", allows us 
747 ! to generate restart files at t=0. 
748 
749 ! Flag to generate restarts at t=0.
750 restart_t0 = .true.
751 
752 ! Get current time in seconds
753 call get_time(atm_int_state%Time_atmos - atm_int_state%Time_atstart, seconds)
754 
755 if (restart_t0 == .true.) then
756   if (seconds == 0) then
757 
758     ! Generate restart files. Same as default block of code in
759     ! subroutine below called "fcst_run_phase_2".   
760     call get_time(atm_int_state%Time_atmos - atm_int_state%Time_atstart, seconds)
761     restart_inctime = set_time(seconds, 0)
762     atm_int_state%Time_restart = atm_int_state%Time_atstart + restart_inctime
763     timestamp = date_to_string (atm_int_state%Time_restart)
764     call atmos_model_restart(atm_int_state%Atm, timestamp)
765     call wrt_atmres_timestamp(atm_int_state,timestamp)
766     print *, 'Restart files at t = 0 seconds generated.'
767 
768   endif
769 endif
770 
771 !-------------------------------------------------------------------------
772 !************************ END MY CHANGES *****************************
773 !-------------------------------------------------------------------------