2. Adding components
Here are the steps to add prognostic components to CIME models.
There are a couple of aspects of a component interface to CIME, the scripts interface which controls setting up component inputs and building the component and the run interface which controls connecting the component to the coupler and through the coupler, the other components of the CIME based model.
The component should have a subdirectory cime_config and this subdirectory should have two files buildnml and buildlib The buildnml script is used to build the components instructional, runtime inputs. These have traditionally been in the form of fortran namelists but may also follow other formats. The buildnml may either be called from the command line or as a python subroutine. If buildnml is called from the command line it will be passed the caseroot directory on the command line. If it is called as a subroutine, the subroutine name must be buildnml and it will take three arguments, a Case object, a caseroot directory and a component name. The buildlib script will always be called from the command line, it is called in the case.build step and is expected to build the the buildlib script will be called with three arguments in order they are caseroot, libroot (the location of the installed library, typically EXEROOT/lib) and bldroot, the location of the component build directory. Look at the cime internal components such as datm for an example.
The coupler interface is dependent on which coupler is used, for the mct coupler in cime the component model must provide NNN_INIT_MCT, NNN_RUN_MCT, NNN_FINAL_MCT where NNN is the component type of the particular component (eg ATM for an atmosphere, LND for a land model) these subroutines are expected to be in the component library.