Change the 'parcel_hscale' parameter in the ZM convection to a namelist parameter

[swrneale]

What is the feature/what would you like to discuss?

It's simple but I'd like to turn the hardwired parameter parcel_hscale Into a namelist parameter.
It's currently in the code here.

! Scaling of PBL height to give parcel mixing length for lparcel_pbl=True

real(kind_phys), parameter :: parcel_hscale = 0.5_kind_phys

The variable is in zm_convr.F90 and it should retain the 0.5 value as default to make it bfb in CAM7
It will make it easier for everyone to carry out sensitivity experiments and add visibility to an important parameter.

Is there anyone in particular you want to be part of this conversation?

Nope. it's a pretty simple change.

Will this change (regression test) answers?

No

Will you be implementing this enhancement yourself?

Any CAM SE can do this