I’m trying to run CMAQ_ISAM but I got an error message in my LOG file(see below), the model doesn’t seem to find ISAM region file. I make sure I provided the right path. Does anyone know why?
Error reading IDs for variable CD CN CB CQ YX
netCDF error number -49 processing file "ISAM_REGIONS"
NetCDF: Variable not found
*** ERROR ABORT in subroutine SubhFile_Cell on PE 001
Could not open ISAM_REGIONS
PM3EXIT: date&time specified as 0
Date&time specified as 0
The errors you posted point to a problem with reading variables from the ISAM_REGIONS file, not with not being able to find the file. Looking at that error message, the code is looking for a variable named “CD CN CB CQ YX” while you probably want it to be looking for five different variables named CD, CN, CB, CQ, and YX. To help us diagnose this further, please post your EmissCtrl file, your isam_control file, and the header of our ISAM_REGIONS file obtained with ncdump -h.
The final error message you encountered “Could not open ISAM_REGIONS” is misleading in this case, I will flag it for the developers to have a look at.
Looking at the header of the ISAM_REGIONS file you posted as ISAM_REGIONS.txt file, it seems the file does not fully comply with I/O API conventions, leading to an error when CMAQ tries to read from it.
Specifically, since variable names in I/O API have a length of 16 characters (including spaces), the VAR-LIST attribute cannot be " CD CN CB CQ YX YD OT " since it needs to contain 16 characters (including spaces) for each variable and have a length of NVARS x 16. You can look at the headers of MCIP files for examples of properly constructed VAR-LIST attributes. It also appears that a number of the attributes in your file that should be of type integer (FTYPE, GDTYP, NVARS, STIME, SDATE, etc.) are of type real which may also cause problems.
Generally, it is strongly advised to use Fortran code linking in the I/O API libraries or programs from I/O API’s M3tools to create CMAQ input files such as this one to ensure that they comply with I/O API standards. There are a number of other threads discussing this topic: