Question about the input aerosol file for CAM5 with bulk aerosol module (E1850C5)

[11438023@zju_edu_cn]

Dear all,

I am using the E1850C5 compset to do some simulations, and I would like to turn off the interactive aerosol to reduce simulation time.

Following previous threads, I changed:

1) CAM_CONFIG_OPTS to "-phys cam5 -chem none" in env_build.xmladd;
2) prescribed_aero_model='bulk' in user_nl_cam

The building process is fine, but I found that in the "./CastDoc/atm_in", the input aerosol file uses the year 2000 data.

I tested F1850C5 and the results are the same with E1850C5.

I also created one case using F1850C5PM. By default, it uses the year 1850 aerosol input data.

I am wondering why E1850C5 uses the year 2000 data? does it give better simulation results for the pre-industrial conditions? or I made some mistakes that I am not aware of?

Thanks very much!

 

[hannay]

The reason is that when you are changing the CAM_CONFIG_OPTS, you are not using a predefined compset anymore.
By default, the model is using the 2000 values. You need to manually change the namelist files to 1850.

You might be able to recover some of the 1850 values by setting CAM_NML_USE_CASE=1850_cam5 in env_run.xml

 

[11438023@zju_edu_cn]

Hi Hannay,

Thanks very much for your suggestions. I have one more minor questions,

1) If I only set CAM_CONFIG_OPTS to "-phys cam5 -chem none" in env_build.xml, the model will use prescribe aerosol in MAM3;

2) If I also set prescribed_aero_model='bulk' in user_nl_cam, the model will use CAM4 bulk aerosols.

The purpose is only to prescribe the aerosol. So do you have any recommendations about which one is better to use?

---

Also, by comparing the above three cases (e1850c5, f1850c5, and f1850c5pm), I found that I can:
1) set CAM_CONFIG_OPTS to "-phys cam5 -chem none" in env_build.xml;
2) set CAM_NML_USE_CASE to"1850_cam5_pm" in env_run.xml.

In this way, the input data is the same between e1850c5, f1850c5, and f1850c5pm.

Thanks again.

Best,
Lei

 

[tilmes]

Hi Lei,
I am not sure from this email string what version of the model you are using. However, in general, using CAM5 means that you are running with the modal aerosol scheme (MAM3 or MAM4) as a default. The modal aerosols are coupled to the clouds and radiation and there is no version that is scientifically supported, wich prescribes aerosols or turns off the aerosols interactions in CAM5. Therefore, I would strongly recommend to not try to do that unless you want to put a lot of effort into this. If you are concerned about model costs you can think about running a version of CESM1 using CAM4 that prescribes aerosols, or think of other ways to reduce costs. This all depends on the science question you are trying to address.
Cheers, Simone

 

[11438023@zju_edu_cn]

Thanks very much!

1) We are using the CESM1.2 version with slab ocean configurations;
2) We want to add additional evaporation from the surface to the atmosphere and see the climate responses.

We used CAM4 for testing before. Since CAM5 improves many processes compared to CAM4, we were thinking to switch to CAM5 at this stage. So maybe we can just stick to CAM4.