Is it possible to start NEMO at 12 UTC?

1

Hi,
Generally NEMO starts running at 00 o’ clock. Now I want to set up a NEMO model for operational forecast starting from 12(UTC), is it possible?
Rui

2

It should work by defining nn_time0 in the namrun part of namelist_cfg. The default definition (in namelist_ref) is:

   nn_time0    =       0   !  initial time of day in hhmm
3

Hi!
Is nn_time0 working properly? I’ve set it 1200 to start model run from 12:00, but run crashes with errors like:

  ===>>> : E R R O R

          ===========

           iom_get_123d, file: path/to/bdy/nbdy_T_2D_y2025m05d05.nc, var: zos
 start and count too big regarding to the size of the data,
 (istart(3) + icnt(3) - 1) =    13
  is larger than idimsz(3) =    12

I have daily files with different frequency (different files for different freqs) for bdy. For first run day data starts from 12:00, so in first file I have only 12 hourly time records. But looks like NEMO wants more. :grinning_face:

4

NEMO probably always expects daily input files to cover the full day, irrespective of whether it will use the full day’s worth of data or not. Try to fill your BDY input with 12 dummy time steps in the beginning (e.g., repeat the 12:00 data for all hours between 00:00 and 11:00), so that the first file also has 24 time steps.

5

Yes I confirm, if you have a daily file with hourly data, we expect your file to have 24 records. For practical issue, NEMO is not trying to get the calendar information that could be available in your input files. NEMO is just using the record numbers to pick-up the appropriate data.

6

@smasson @cpelletier Thank you for your answer!
I truncated the data in the hope that it might help to get an output file with the start of the data recordings at 12 UTC in output file. Is this possible in NEMO?