Possible combination of WACCM / CAM / radiation parameterization

[swahl@geomar_de]

Dear all

today we discussed what combinations of WACCM / CAM and radiation parameterization are actually possible in CESM 1.2.0. We stumbled upon this as we figured out that after we did a setup with the B_1955-2005_WACCM_CN compset that this compset uses "cam4" CAM version and "camrt" as the radiation parameterization. However we where expecting to have CAM5 and the new RRTMG radiation parameterization to be used. So the question is:
- Is it actually possible to run WACCM with CAM5 and RRTMG ratiation parameterization or is this setup not yet ready (or not tuned to be stable)?
( Which combinations of WACCM / CAM / radiation parameterizations are valid and tested? )
This doesn't get clear in the Users Guide.

Thanks very much for your help and comments

Sebastian

 

[santos]

I am moving this to the WACCM forum, as this is rather WACCM-specific.WACCM4 (WACCM + CAM4) is currently the only supported WACCM configuration, which I believe is why this is not addressed in the User's Guide. There is not much flexibility here.WACCM5 (WACCM + CAM5) exists as a development preview in CESM 1.2, but it has some issues that cause intermittent crashes (as frequently as every few years for transient test cases), and there are not many compsets defined for it (only 1850 and year 2000). Some of the code issues may be fixed in an upcoming version (CESM 1.2.2), but there will still not be any supported 1955-2005 compsets. There's a significant possibility that we will never tune up a fully supported WACCM5, instead focusing resources on ensuring that WACCM6 is ready at the same time as CAM6.A third option is WACCM4 + RRTMG. This can be run by setting up a normal WACCM4 case, but adding "-rad rrtmg" to CAM_CONFIG_OPTS. We don't officially provide support for this either, but it is the easiest way to run RRTMG with WACCM that's likely to work, and some individuals have used this in the past. In this case, everything but the radiation will be as in WACCM4, so there is no change in vertical grid, no MAM, no updated cloud physics, etc.

 

[santos]

I am moving this to the WACCM forum, as this is rather WACCM-specific.WACCM4 (WACCM + CAM4) is currently the only supported WACCM configuration, which I believe is why this is not addressed in the User's Guide. There is not much flexibility here.WACCM5 (WACCM + CAM5) exists as a development preview in CESM 1.2, but it has some issues that cause intermittent crashes (as frequently as every few years for transient test cases), and there are not many compsets defined for it (only 1850 and year 2000). Some of the code issues may be fixed in an upcoming version (CESM 1.2.2), but there will still not be any supported 1955-2005 compsets. There's a significant possibility that we will never tune up a fully supported WACCM5, instead focusing resources on ensuring that WACCM6 is ready at the same time as CAM6.A third option is WACCM4 + RRTMG. This can be run by setting up a normal WACCM4 case, but adding "-rad rrtmg" to CAM_CONFIG_OPTS. We don't officially provide support for this either, but it is the easiest way to run RRTMG with WACCM that's likely to work, and some individuals have used this in the past. In this case, everything but the radiation will be as in WACCM4, so there is no change in vertical grid, no MAM, no updated cloud physics, etc.