3: Modify wind stress

Wind stress plays a critical role in driving ocean currents and is a key factor in shaping the overall patterns of large-scale ocean circulation and, consequentialy, the climate. Further details on how wind stress affects the ocean circulation are discussed in this manuscript.

Exercise: Increase zonal wind stress

Create a case called g.GW_JRA.TL319_t233_wg37.003 using the compset GW_JRA at TL319_t233_wg37 resolution.

Verify that the run length is set to 1 year.

Modify the subroutine mom_import in mom_cap_methods.F90 to increase the zonal (x) component of the wind stress by 25%.

Build and run the model for one year.

Compare the simulations using ncview/ncdiff, etc.

Click here for hints

Where is the source code?

You can find mom_cap_methods.F90 in /glade/u/home/$USER/cesm.code/cesm3_0_alpha09b/components/mom/MOM6/config_src/drivers/nuopc_cap/

How do I compile and run?

You can compile with the command:

qcmd -- ./case.build

You can run with the command:

./case.submit

How do I check the lenght of the run?

Use xmlquery to search for the variables that control the run length

Click here for the solution

Clone a new case g.GW_JRA.TL319_t233_wg37.003 from your control experiment with the command:

cd /glade/u/home/$USER/code/my_cesm_code/cime/scripts/
./create_newcase --case /glade/u/home/$USER/cases/g.GW_JRA.TL319_t233_wg37.003 --compset GW_JRA --res TL319_t233_wg37 --run-unsupported

Case setup:

cd /glade/u/home/$USER/cases/g.GW_JRA.TL319_t233_wg37.003
./case.setup

Verify that the run length is 1 year:

./xmlquery STOP_N
./xmlquery STOP_OPTION

Copy the mom_cap_methods.F90 file from the control case to the ocean SourceMods.

cp /glade/u/home/$USER/code/my_cesm_code/components/mom/MOM6/config_src/drivers/nuopc_cap/mom_cap_methods.F90 /glade/u/home/$USER/cases/g.GW_JRA.TL319_t233_wg37.003/SourceMods/src.mom/

Edit the file mom_cap_methods.F90 in the mom_import subroutine after taux is defined (line 164):

  taux(:,:) = taux(:,:) * 1.25

If needed, change job queue and account number. For instance:

./xmlchange JOB_QUEUE=tutorial,PROJECT=UESM0016 --force

Build and submit:

qcmd -- ./case.build
./case.submit

When the run is completed, look into the archive directory for: g.GW_JRA.TL319_t233_wg37.003.

cd /glade/derecho/scratch/$user/archive/g.GW_JRA.TL319_t233_wg37.003/ocn/hist
ls 

Test your understanding

• What are the impacts of increased zonal wind stress?

• Where do you think the impacts would be largest in the ocean?

• How do you think the changes would compare if you increased meridional wind stress?