Does anyone have experience with the variables PCLDTOP and PCLDBOT in CAM history files? I am trying to understand how these are defined. The history files and the documentation describe these as "pressure of cloud top" and "pressure of cloud base", but list the units as "1". The numerical values look to me like they could be in pascals, but when I plot the two (in zonal average), they cross--which is very confusing. Can't help but wonder if I'm missing something...
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How are PCLDTOP and PCLDBOT defined?
- Thread starter rdeitrick
- Start date
Hi Russell,
PCLDTOP/PCLDBOT and likewise CLDTOP/CLDBOT are the pressure (in Pa) and vertical index of the top and bottom of in-plume clouds in the convection schemes. If you are running CAM4/CAM5, then it the TOP and BOT refer to highest and lowest cloud of the shallow and deep convection scheme. If you are running CAM6, where CLUBB does shallow convection, this metric is exclusive to the deep convection scheme --it does not contain any information about the vertical extent of CLUBB.
I did catch that the units "1" were wrong, so I've changed that in most recent version of the CAM code, so it says Pa.
PCLDTOP/PCLDBOT and likewise CLDTOP/CLDBOT are the pressure (in Pa) and vertical index of the top and bottom of in-plume clouds in the convection schemes. If you are running CAM4/CAM5, then it the TOP and BOT refer to highest and lowest cloud of the shallow and deep convection scheme. If you are running CAM6, where CLUBB does shallow convection, this metric is exclusive to the deep convection scheme --it does not contain any information about the vertical extent of CLUBB.
I did catch that the units "1" were wrong, so I've changed that in most recent version of the CAM code, so it says Pa.
Hi Adam,
Thanks for that! I suspected that those variables had something to do with just the convective clouds, but I wasn't sure. The fact that the two values cross (PCLDBOT < PCLDTOP)--this happens at mid- to high-latitudes, where convection is probably not occurring regularly, I would guess--does this just mean that the two values don't really mean anything at those latitudes because convection is suppressed?
Thanks!
Thanks for that! I suspected that those variables had something to do with just the convective clouds, but I wasn't sure. The fact that the two values cross (PCLDBOT < PCLDTOP)--this happens at mid- to high-latitudes, where convection is probably not occurring regularly, I would guess--does this just mean that the two values don't really mean anything at those latitudes because convection is suppressed?
Thanks!
Hi Russell,
I think you may have found a bug. I've opened a git issue here: CLDTOP/CLDBOT pbuf variables initialized incorrectly · Issue #605 · ESCOMP/CAM
Thanks,
Adam
I think you may have found a bug. I've opened a git issue here: CLDTOP/CLDBOT pbuf variables initialized incorrectly · Issue #605 · ESCOMP/CAM
Thanks,
Adam
Russell, if you're interested in trying out a fix I came up with, email me at aherring@ucar.edu.
Hi Adam, thanks for doing that. I'm looking at the github issue--you all work really quickly!
For your fix, would I need to change the source code? I am really new to CESM and using a pre-installed version on Compute Canada. So if I need to modify the source it might be a challenge for me. Anyway, if you've been able to replicate the issue, then you might not need me. I don't actually need these variables in my current project, I just noticed that they looked strange. But if you do need me to try something or to provide details, just let me know as I'd like to help.
For your fix, would I need to change the source code? I am really new to CESM and using a pre-installed version on Compute Canada. So if I need to modify the source it might be a challenge for me. Anyway, if you've been able to replicate the issue, then you might not need me. I don't actually need these variables in my current project, I just noticed that they looked strange. But if you do need me to try something or to provide details, just let me know as I'd like to help.
Hi Russell,
It does require adding a single line to the source code, although you don't need to modify the source code as you can just copy the modified module into SourceMods/src.cam/ in your case directory. As you're a new user, what I said probably makes no sense to you ;) Nonetheless, feel free to reach out if you want this fix. Either way, I'll just take care of it when I take care of it.
It does require adding a single line to the source code, although you don't need to modify the source code as you can just copy the modified module into SourceMods/src.cam/ in your case directory. As you're a new user, what I said probably makes no sense to you ;) Nonetheless, feel free to reach out if you want this fix. Either way, I'll just take care of it when I take care of it.