Is it possible to modify a parameter in the physics parameterization without rebuilding a case?

[teopb]

Hello,

I would like to run a model with a variety of values for a parameter sequentially. For example in the Held Suarez model (FHS94) there is a parameter "efolda". I would like to make a run with efolda = 30._r8, then based on the output of that run it again with a new value. As "efolda" is not a namelist variable I don't think I can change it that way. I could make a source mod of held_suarez.F90 with the new value but then I would have to rebuild each time (right?) which takes a long time relative to my model runs. Is there a better way to do this? I have been searching the documentation to no avail.

Thank you!

 

[cacraig]

The value of efolda is indeed only a hardcoded parameter in the Held-Suarez model. As it stands right now, the only way you can change its value is to modify it in the source code and then recompile. That said, the case.build command is "smart" and when rerun, will only compile the portion of the code which is modified and will compile much more quickly than starting from scratch.

If you want to make this runtime configurable, it will take a non-trivial amount of code modification to set this up as a namelist variable. Since Held-Suarez does not have a namelist, you will not only need to add the variable to the namelist build system, but you would also need to add a subroutine to read a new namelist you create and call it within the code. Unfortunately, the procedure for adding a namelist variable is not documented anywhere. If this is a project that you will be using over and over for quite awhile, it might be worth investing the time into making the modifications.

 

[teopb]

Thank you.