The GRIDCRO3D file is not generated by MCIP. What may be the cause?
GRIDCRO3D is only created when MCIP is used to process MM5 data. The fields in GRIDCRO3D are X3HT0F and X3HT0M, which are the heights on full levels and mid-levels; they are static in time with MM5. In WRF, however, the layer heights change with time. The time-varying layer heights are stored in the METCRO3D arrays ZF and ZH.
This information is very helpful, thank you. Is it a good practice then to replace GRIDCRO3D by METCRO3D in CCTM simulations? I am guessing that CGRID is generated by CCTM when one of these two files is provided.
CMAQ is already configured to get what it needs from METCRO3D. If you are running with WRF, CMAQ is not expecting you to have a GRIDCRO3D file.