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_windstress by cloning the control experiment case.

Verify that the run length is set to 1 year.

Modify the subroutine rotate_wind_stress in forcing_coupled.F90 to increase the first (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

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_windstress from your control experiment with the command:

cd /glade/work/$USER/code/my_cesm_code/cime/scripts/
./create_clone --case /glade/work/$USER/cases/g_windstress --clone /glade/work/$USER/cases/g_control

Case setup:

cd /glade/work/$USER/cases/g_windstress
./case.setup

Verify that the run length is 1 year:

./xmlquery STOP_N
./xmlquery STOP_OPTION

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

cp /glade/work/$USER/code/my_cesm_code/components/pop/source/forcing_coupled.F90 /glade/work/$USER/cases/g_windstress/SourceMods/src.pop

Edit the file forcing_coupled.F90 in the rotate_wind_stress routine after SMFT(:,:,1,:) is defined:

 SMFT(:,:,1,:) = SMFT(:,:,1,:) * 1.25

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

./xmlchange JOB_QUEUE=regular,PROJECT=UESM0011

Build and submit:

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

When the run is completed, look into the archive directory for: g_windstress.

(1) Check that your archive directory on cheyenne (The path will be different on otehr machines):

cd /glade/scratch/$user/archive/g_windstress/ocn/hist
ls

Test your understanding#

  • What are the impacts of increased zonal wind stress?

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

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