CAM4 with microphysics mg1

[pbreul]

Hi everyone,

I am running CAM4 on CESM2.1.3, but would like to have a better Aerosol-Cloud Interaction. I therefore tried to change the microphysics package to the one developed for CESM5, by running: ./xmlchange --append CAM_CONFIG_OPTS='-microphys mg1'.

I can build the case, however when running I get the error "ERROR: Attempt to find undefined name in pbuf CICEWP" in the CESM/CAM log file.

Is what I am trying to do not possible, or do I have to adjust additional settings?

I am thankful for any suggestions :).

Best wishes,
Philipp

 

[brianpm]

Hi Phillipp --

Well, I would say that what you want to do is *possible*, but it's probably not as easy as changing CAM_CONFIG_OPTS. I feel like there are a bunch of places throughout physpkg.F90 where there are checks to figure out what model physics and/or what microphysics are being used. The division of work between "microphysics" and "macrophysics" changed quite a bit between CAM4 and CAM5, so I don't think the issue is as easy as just running the MG microphysics in CAM4; I suspect that the "grid scale condensation/evaporation" (i.e., macrophysics) would have to be handled differently too.

The specific issue you are seeing, I think has to do the additional fields that the MG microphysics needs to use (in-cloud water paths in this case). Probably you're seeing this because physpkg is running the wrong microphysics initialization, but that's just a guess.


Honestly, I think if you're interested in aerosol-cloud interaction effects, it might be more fruitful to start from a model that has ACI (CAM5 or CAM6) and then make changes to remove the ACI. But depends on your application whether that makes sense.

 

[pbreul]

Hi Brian,

Thank you for the very insightful comment, at least I know now that there is no easy fix.
My problem is that I already have a bunch of experiments with a specific custom component set (using CAM4) and would ideally keep everything as close as possible to this component set. For a new set of experiments I however need some representation of aerosol-cloud interactions, which the rk microphysics does not have at all as far as I understand?

I will have a think what the most sensible way forward is for me and will probably post some follow up question no matter which route I take :D.

Thanks a lot.

Philipp

 

[yinjiyuan]

Hi Phillipp --

Well, I would say that what you want to do is *possible*, but it's probably not as easy as changing CAM_CONFIG_OPTS. I feel like there are a bunch of places throughout physpkg.F90 where there are checks to figure out what model physics and/or what microphysics are being used. The division of work between "microphysics" and "macrophysics" changed quite a bit between CAM4 and CAM5, so I don't think the issue is as easy as just running the MG microphysics in CAM4; I suspect that the "grid scale condensation/evaporation" (i.e., macrophysics) would have to be handled differently too.

The specific issue you are seeing, I think has to do the additional fields that the MG microphysics needs to use (in-cloud water paths in this case). Probably you're seeing this because physpkg is running the wrong microphysics initialization, but that's just a guess.


Honestly, I think if you're interested in aerosol-cloud interaction effects, it might be more fruitful to start from a model that has ACI (CAM5 or CAM6) and then make changes to remove the ACI. But depends on your application whether that makes sense.

Hi! May I ask how to remove the impact of ACI? How should the namelist be set up? Thank you !