Forcing PORT with CMIP6 output?

[CalvinC]

Hi all!

I am new to using the Parallel Offline Radiative Transfer configuration of CAM, so please excuse me if this is a simple question. From what I understand, PORT is an offline radiative transfer model that uses the CAM radiation code. I am currently using the CAM6 version, built from CESM2.1.5 on a linux based HPC cluster.

So far everything I have read about PORT leads me to believe that I need to force PORT with output created by a full CESM or CAM run. To do this I would need to set rad_data_output = .true. in the CAM namelist to get all of the necessary radiation forcing fields. My question is this: is it not possible to take CMIP6 output of atmospheric profiles of T/Q/cloud fields etc. from piControl and 4xCO2 runs to force PORT?

Additionally, if I want to perform sensitivity testing, can I change individual fields (like surface albedo) manually?

Basically, getting and setting the input data for PORT seems to be an involved and not manual process, but I'm wondering if I'm misunderstanding. So far I've read the paper introducing PORT (https://gmd.copernicus.org/articles/6/469/2013/gmd-6-469-2013.pdf), the section in the CAM7 documentation on PORT (4. Atmospheric configurations (compsets) — camdoc documentation) and the NCAR wiki page (PORT - PORT - Parallel Offline Radiative Transfer Tool for CAM - wiki.ucar.edu). Are there other documentation resources I should know about?

Thanks in advance for any responses/discussion! I appreciate it a lot.
Calvin

 

[hplin]

Hi CalvinC, thanks for writing.

I agree that PORT needs to be forced with output from a full CESM/CAM run by setting rad_data_output = .true. - looking at the code (src/physics/cam/radiation_data.F90) rad_data_output = .true. will enable a series of output fields to be written into the CAM history file, e.g., rad_asdir (radiation input: short wave direct albedo), rad_asdif (radiation input: short wave difuse albedo), rad_aldir (radiation input: long wave direct albedo), ... which are then read by the PORT simulation in the rad_data_read subroutine in the same radiation_data.F90. These fields are not output by default, so it might not be possible to use the CMIP6 outputs directly, but you may be able to reproduce the runs then enable rad_data_output = .true. to get the necessary inputs.

As mentioned above there appears to be albedo fields in the history file written by rad_data_output = .true. so you may be able to change them for sensitivity simulations.

Hope this is helpful!