CESM2-CMIP5 experiments

The CESM2 with CMIP5 forcing is a publicly available set of climate model simulations intended to disentangle the role of forcing versus model structure between CESM2 and CESM1 for pre-industrial, 20th and 21st centuries simulations.

A description of the project is available at: https://www.cesm.ucar.edu/community-projects/cesm2-cmip5

The current repository contains the model code and case setups for the CESM2-CMIP5 Forcing Experiment. It also contains the namelists for the CESM1, CESM2 and CESM2-CMIP5 experiments to allow a comparison between them.

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Comparing namelists for CESM1, CESM2 and CESM2-CMIP5 experiments

To obtain the namelists of the CESM1, CESM2 and CESM2-CMIP5 experiments, you need to do the following :

git clone https://github.com/NCAR/CESM2-CMIP5  --branch namelists  namelists

Model code to run the CESM2-CMIP5 experiments

To obtain the CESM code you need to do the following:

1. Clone the repository :

   git clone https://github.com/NCAR/CESM2-CMIP5 --branch cesm2-cmip5-tag  cesm2-cmip5-tag 

This will create a directory cesm2-cmip5-tag in your current working directory.

2. Go into the created directory and check out the externals :

   cd cesm2-cmip5-tag
   ./manage_externals/checkout_externals 

Case directories of the CESM2-CMIP5 experiments

The case directories of the following CESM2-CMIP5 experiments are available :

b.e21.B1850.f09_g17.cesm2-cmip5.001: pi-control (500 years)
b.e21.BHIST.f09_g17.cesm2-cmip5.001: historical (1850-2005)  
b.e21.BRCP85.f09_g17.cesm2-cmip5.001: rcp85 (2006-2100)
b.e21.BRCP85.f09_g17.cesm2-cmip5.101: rcp85 (2006-2100) with bugfix for num_a2

To obtain a specific case directory (for instance: b.e21.B1850.f09_g17.cesm2-cmip5.001), you need to do the following :

git clone https://github.com/NCAR/CESM2-CMIP5 \
--branch b.e21.B1850.f09_g17.cesm2-cmip5.001  b.e21.B1850.f09_g17.cesm2-cmip5.001

More details about the setting of the B1850, BHIST and RCP85 ==============================================

B1850

The pi_control b.e21.B1850.f09_g17.cesm2-cmip5.001 starts as an hybrid run from:

• RUN_REFCASE=b.e21.B1850.f09_g17.CMIP6-piControl.001
• RUN_REFDATE=0501-01-01

The pi_control is 500 years.

BHIST

The b.e21.B1850.f09_g17.cesm2-cmip5.001 starts as an hybrid run from the pi-control at year 250:

• RUN_REFCASE=b.e21.B1850.f09_g17.cesm2-cmip5.001
• RUN_REFDATE=0250-01-01

Due to computational constraints,

• only the first historical ensemble member b.e21.BHIST.f09_g17.cesm2-cmip5.001 runs from 1850-2005,
• the remaining members b.e21.BHIST.f09_g17.cesm2-cmip5.002, ... b.e21.BHIST.f09_g17.cesm2-cmip5.010 were started at 1920 from the first member with a pertlim perturbation.

RCP85

The b.e21.RCP85.f09_g17.cesm2-cmip5.001 starts as an hybrid run from the historical run b.e21.BHIST.f09_g17.cesm2-cmip5.001 at year 2006:

• RUN_REFCASE=b.e21.BHIST.f09_g17.cesm2-cmip5.001
• RUN_REFDATE=2006-01-01

Similarly, ensemble 2-10 starts from:

• b.e21.BHIST.f09_g17.cesm2-cmip5.002 => b.e21.RCP85.f09_g17.cesm2-cmip5.002
• ...
• b.e21.BHIST.f09_g17.cesm2-cmip5.010 => b.e21.RCP85.f09_g17.cesm2-cmip5.010

RCP85 + bugfix

The b.e21.RCP85.f09_g17.cesm2-cmip5.101 starts as an hybrid run from the historical run b.e21.BHIST.f09_g17.cesm2-cmip5.001 at year 2006: - RUN_REFCASE=b.e21.BHIST.f09_g17.cesm2-cmip5.001 - RUN_REFDATE=2006-01-01

This run is similar to b.e21.RCP85.f09_g17.cesm2-cmip5.001 but includes a bugfix for the _a2 emissions aerosol emissions. The influence of the incorrect _a2 emissions on climate properties was found to be minimal.