Change the date in an ESM1.6 restart

Earth System Earth System Model
1

These instructions outline how to change the model date in an ACCESS-ESM1.6 restart. The restart for each component needs to be updated seprately.

Atmosphere:

Navigate to the restart/atmosphere directory

module use /g/data/xp65/public/modules
module load conda/analysis3

# Update the date in the UM dump file
python ~access/apps/pythonlib/umfile_utils/access_cm2/change_dump_date.py restart_dump.astart  <<< "YYYY MM DD"
# Update the date in the calendar file
sed -i "s/end_date:.*/end_date: YYYY-MM-DD 00:00:00/" <new-restart-path>/atmosphere/um.res.yaml

Ocean:

In the restart/ocean directory, edit ocean_solo.res:

     3        (Calendar: no_calendar=0, thirty_day_months=1, julian=2, gregorian=3, noleap=4)
     1     1     1     0     0     0        Model start time:   year, month, day, hour, minute, second
  2145     1     1     0     0     0        Current model time: year, month, day, hour, minute, second

Replace the date in the 3rd line, taking care to preserve the column alignment. The entries should not be zero-padded.

Ice:

In the restart/ice directory:
Rename the iced.YYYY-MM-DD-00000.nc to use the new date. The year, month, and day should be zero padded. Edit the ice.restart pointer file to use the new file name:

echo ./RESTART/iced.YYYY-MM-DD-00000.nc   >  ice.restart_file

Replace the year, nyr, month, and mday global attributes using nco (in most cases, only the year will need to be changed):

module load nco
ncatted -O -a year,global,o,l,<YYYY> iced.YYYY-MM-DD-00000.nc
ncatted -O -a nyr,global,o,l,<YYYY> iced.YYYY-MM-DD-00000.nc
ncatted -O -a month,global,o,l,<MM> iced.YYYY-MM-DD-00000.nc
ncatted -O -a mday,global,o,l,<DD> iced.YYYY-MM-DD-00000.nc

Replace the time global attribute to equal the total number of seconds between 1/1/1 and the new date using the proleptic Gregorian calendar. This can be calculated using the cftime python library. E.g. using 2105-03-01 as the new date:

python 
>>> import cftime
>>> start = cftime.datetime(1,1,1, calendar="proleptic_gregorian")
>>> end = cftime.datetime(2105,3,1, calendar="proleptic_gregorian")
>>> (end-start).total_seconds()

66400905600.0

Then use nco to add this to the restart file:

ncatted -O -a time,global,o,d,66400905600 iced.YYYY-MM-DD-00000.nc
2 Likes
2

@spencerwong - thanks for the instructions, which I appear to have followed successfully.
I did note that in the ice section the ‘echo’ command should be > ice.restart_file
Also, as a non-python user, I had to guess how to get out of the python command for calculating the number of seconds.
If easy, it might be good to bundle all of this into a single script with the user just having to provide the new date.

1 Like
3

Thanks @RachelLaw, I’ve corrected the instructions