TauLock_CESM

% Edited December 2023

This directory provides modified source code files for CESM 1.2.2.1 to implement the interannually-varying wind stress overriding protocol introduced in Luongo et al. (2022) and the climatological wind stress overriding protocol introduced in Luongo et al. (In Review).

If using the source code for the interannually-varying wind stress overriding, please cite the following references (for both the article and the code itself):

1. Luongo, M.T., Xie, S.-P., and Eisenman, I., 2022. Buoyancy Forcing Dominates the Cross-Equatorial Ocean Heat Transport Response to Northern Hemisphere Extratropical Cooling. Journal of Climate, 35(20), pp. 3071-3090. doi: https://doi.org/10.1175/JCLI-D-21-0950.1

2. Luongo, M.T., Xie, S.-P., Eisenman, I., 2022. GCM Modification Code from: Buoyancy Forcing Dominates the Cross-Equatorial Ocean Heat Transport Response to Northern Hemisphere Extratropical Cooling. UC San Diego Library Digital Collections. doi: https://doi.org/10.6075/J09P31TF

Here, I provide a quick README to make heads or tails of these mods. If you want to see the few dozen lines out of the many thousands of lines of base code that I changed to create this protocol, I suggest just searching "Luongo" in the files. I tried to comment near each line with my name and the date.

First, you'll notice there are three sub-directories, CPLOutput, TauLock, and ClimTauLock. I'll go through each of these below sequentially.

1. CPLOutput: In order to lock wind stress in CESM, you need to output wind stress from a case first. Let's say you call this case "ControlCase." After you run ./cesm_setup but before you run ./ControlCase.clean_build, you need to copy CPLOutput/src.drv/ccsm_comp_mod.F90 to your SourceMods/src.drv directory in the case directory. After you build and run this case, the introduced mod should output a file every simulated day called ControlCase.cpl.x2o_oo.YY-MM-DD-01800.nc. These files will be in your /glade/scratch/USER/ControlCase/run/ directory, are about 35Mb per day, and include all variables that the coupler passes to the ocean.

2. TauLock: This code is for interannually-varying wind stress overriding. Now that you've output daily wind stress from ControlCase, you'll want to input it into ExperimentalCase. After set-up, copy TauLock/src.drv and TauLock/src.pop2 to your SourceMods/src.drv and SourceMods/src.pop2 directories in the caseroot, respectively. Keep in mind that there are some specifics you'll need to change in ccsm_comp_mod.F90 -- I've written USER and OUTPUTCASENAME in the file, but you'll need to correct the path and the file names for your case. These mods will take in the output wind stress from ControlCase at each coupling step (around 12:30am in the modeled day I believe) and exactly specify wind stress over the ocean in ExperimentalCase.

3. ClimTauLock: This code is for climatological wind stress overriding. After outputting daily wind stress from ControlCase, you need to create a daily climatology of the wind stress files. You can do this using a bash loop and the NCO command "ncea." You should end up with 365 files, one for each day of the year. I recommend naming your daily climatology files ControlCase.cpl.x2o_oo.MM-DD-01800.nc to minimize code edits. You then follow the directions above for the TauLock case. The major difference between ClimTauLock/src.drv/ccsm_comp_mod.F90 and TauLock/src.drv/ccsm_comp_mod.F90 is that in the former the file names are not allocated to include a year in their string.

Note that these mods of course don't change some of the other specifics for your CESM1.2 case (resubmission, run type, compset, etc.). I usually write a big bash script to do it all in a streamlined flow.

Please reach out to me at mluongo(at)ucsd(dot)edu if you have any questions about these code modifications or the workflow.

Matt Luongo

Scripps Institution of Oceanography, UCSD

La Jolla, CA, USA

September 2022, Edited December 2023