Run ROMS

The code here is also available as a notebook 03_run_roms.ipynb.

Run ROMS with 4 CPUs splitting the domain in 2 by 2 tiles

using Dates
using ROMS

Now we are ready to run the model:

modeldir = expanduser("~/ROMS-implementation-test")
simulationdir = joinpath(modeldir,"Simulation1");

Run ROMS from julia

NtileI and NtileJ must match the values in the roms.in file.

NtileI = 1
NtileJ = 1
np = NtileI*NtileJ

use_openmp = true
logfile = "roms.out"

cd(simulationdir) do
    withenv("OPAL_PREFIX" => nothing) do
        ROMS.run_model(modeldir,"roms.in"; use_openmp, np, stdout = logfile)
    end
end;

If you run into a problem, please first read the error message carefully to get some indicaton what is wrong.

The ROMS outputs are the files roms_his.nc and roms_avg.nc.

Note that the usual method to run ROMS is from the command line.

Run ROMS in serial

For example the serial binary romsS (without MPI and OpenMP) can be run as:

./romsS < roms.in | tee roms.out

Run ROMS in parallel

Make sure to activate MPI or OpenMP and recompile ROMS if necessary With MPI:

mpirun -np 4 ./romsM  roms.in | tee roms.out

where 4 is the number of cores to use. To use 4 CPUs, you need to set NtileI to 2 and NtileJ to 2.

With OpenMP:

OMP_NUM_THREADS=4 ./romsO < roms.out | tee roms.out

With the command tee the normal screen output will be place in the file roms.out but still be printed on the screen.

Interpreting ROMS output

• Check minimum and maximum value of the different parameters

 NLM: GET_STATE - Read state initial conditions,             t = 57235 00:00:00
                   (Grid 02, File: roms_nest_his.nc, Rec=0182, Index=1)
                - free-surface
                   (Min = -4.63564634E-01 Max = -3.63838434E-01)

• The barotropic, baroclinic and Coriolis Courant number should be smaller than 1

 Minimum barotropic Courant Number =  2.09670689E-02
 Maximum barotropic Courant Number =  5.56799674E-01
 Maximum Coriolis   Courant Number =  1.71574766E-03

• Information
  • energy (kinetic, potential, total) and volume
  • maximum Courant number

   STEP   Day HH:MM:SS  KINETIC_ENRG   POTEN_ENRG    TOTAL_ENRG    NET_VOLUME  Grid
          C => (i,j,k)       Cu            Cv            Cw         Max Speed

 346200 57235 00:00:00  2.691184E-03  1.043099E+04  1.043099E+04  6.221264E+13  01
          (079,055,30)  9.266512E-02  4.949213E-02  0.000000E+00  1.081862E+00

Plot some variables like sea surface height and sea surface temperature at the beginning and the end of the simulation. In Julia, force figure 1 and to 2 to have the same color-bar.

figure(); p1 = pcolor(randn(3,3)); colorbar()
figure(); p2 = pcolor(randn(3,3)); colorbar()
p2.set_clim(p1.get_clim())

• If everything runs fine,
  • is the model still stable with a longer time steps (DT) ?
  • increase the number of time steps (NTIMES)
  • possibly adapt the frequency at which you save the model results (NHIS, NAVG,NRST)