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You can get the CESM source code with MOSAIC by executing the following commands:

cd your_code_directory
git clone https://github.com/ESCOMP/CAM -b zz_cam6_3_018_mosaic_branch cesm_src_cam6_3_018_mosaicmosaic0.3 your_mosaic_directory
cd cesm_src_cam6_3_018_mosaic

April 2024: the current tag has references to SVN that need to be changed to GIT.  Edit Externals_CAM.cfg (update from svn to git, and change cosp to 'required = False').  

Diff between original and corrected files:

----
3,4c3,4
< protocol = svn
< repo_url = https://svn-ccsm-models.cgd.ucar.edu/tools/proc_atm/chem_proc/release_tags
---
> protocol = git
> repo_url = https://github.com/ESCOMP/CHEM_PREPROCESSOR.git
10,12c10,12
< protocol = svn
< repo_url = https://svn-ccsm-models.cgd.ucar.edu/carma/release_tags
< tag = carma3_49_rel
---
> protocol = git
> repo_url = https://github.com/ESCOMP/CARMA_base.git
> tag = carma4_01
17,20c17,21
< protocol = svn
< repo_url = https://github.com/CFMIP/COSPv2.0/tags/
< tag = v2.1.4cesm/src
< required = True
---
> protocol = git
> repo_url = https://github.com/CFMIP/COSPv2.0
> sparse = ../.cosp_sparse_checkout
> tag = v2.1.4cesm
> required = False
---

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your_mosaic_directory
./manage_externals/checkout_externals

'your_code_directory' should be a directory in your home or work space where you keep CESM source code.  Replace 'your_mosaic_directory' with an appropriate name that reflects this source code.  

You will get a message "You are in 'detached HEAD' state. ..." which is fine.  The mosaic code is not on the main code trunk.

April 2024: the tag "zz_cam6_3_018_mosaic0.3" includes updates replacing SVN with GIT protocols.

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CESM tutorials should be helpful if you are not familiar with CESM/CAM-chem, and how to set up a case from the code.

There is not a compset for the MOSAIC scheme so you must make the changes listed below.  Start with a CAM-chem compset (such as FCnudged).

Create new case

After creating a new case in the usual way (use compset FCnudged), issue the following commands in your new case directory (for running on Derecho):

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• The current CAM-chem/MOSAIC was implemented in CAM6.3.018, which is similar to the CESM2.2 public version but with some minor updates made to CAM. 
• We have only used it using the "FCnudged" compset. No other compsets have been tested yet. FHIST compset will not work. 
• You should use "MAM4" to use MOSAIC at this moment, since some parts of the code were hard coded to MAM4 (MAM3, MAM5 and MAM7 are not compatible with MOSAIC). We are hoping that it can be more flexible in the future when MOSAIC is available in the default version.

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