2. Aerosol diagnostics and output

2.1. Configuring a run with more aerosol diagnostics in NorESM2

To run NorESM2 with more aerosol diagnostics add to user_nl_cam:

&phys_ctl_nl
  history_aerosol = .true.

Adding history_aerosol = .true. to user_nl_cam gives additional 577 variables (+ ca. 13 % CPU-time). Please see an overview of additional output varibales: history_aerosol extra output

2.2. Decomposition of aerosol direct, semidirect and indirect radiative forcing

For effective radiative forcing estimates, multiple calls to the radiation code are necessary (see Ghan et al. 2012 for a detailed explanation). To enable this, copy the file preprocessorDefinitions.h from to the SourceMods/src.cam/ folder in your case directory:

cp <noresm_base>/components/cam/src/physics/cam_oslo/preprocessorDefinitions.h <case_folder>/SourceMods/src.cam/.

To change the preprocessor definition to true, i.e. replace:

#undef AEROFFL

with:

#define AEROFFL

in the preprocessorDefinitions.h file.

The AEROFFL-token tells the model to do additional radiation-diagnostics for aerosol indirect effect. Including #define AEROFFL to preprocessorDefinitions.h gives 8 additionally variables (+ ca. 5% CPU-time). Please see an overview of the additional output variables: AEROFFL extra output

2.3. Enable diagnostics for AEROCOM

NorESM2 can be set up to take out additional aerosol output for use in AeroCom (https://aerocom.met.no/index.html) or other studies where there is a need for extensive aerosol diagnostics. To enable this, copy the file preprocessorDefinitions.h from to the SourceMods/src.cam/ folder in your case directory:

cp <noresm_base>/components/cam/src/physics/cam_oslo/preprocessorDefinitions.h <case_folder>/SourceMods/src.cam/.

To change the preprocessor definition to true, i.e. replace:

#undef AEROCOM

with:

#define AEROCOM

in the preprocessorDefinitions.h file.

If #define AEROCOM is activated, we additionally get 149 variables (+ ca. 13% CPU-time). Please see an overview of the additional output variables: AEROCOM extra output

The model may be run with any combination of these options: with AEROFFL only, with AEROCOM only, or with AEROFFL and AEROCOM activated at the same time.

2.4. References

Ghan, S.J., X. Liu, R.C. Easter, R. Zaveri, P.J. Rasch, J. Yoon, and B. Eaton, 2012: Toward a Minimal Representation of Aerosols in Climate Models: Comparative Decomposition of Aerosol Direct, Semidirect, and Indirect Radiative Forcing. J. Climate, 25, 6461–6476, https://doi.org/10.1175/JCLI-D-11-00650.1