I am currently learning how to use the ISAM module in CMAQ. Although I have gone through the GitHub documentation, I still have some questions that I hope you could help me with. I would appreciate it.
According to the requirements, I need to provide GRIDMASK.nc (ISAM_REGIONS file) from IOAPI. However, since I am not familiar with IOAPI, I would like to know if there are any convenient methods to create the GRIDMASK file, perhaps using Python? As of now, I can only modify variable names and values based on the GRIDCRO2D file generated by MCIP, which is quite limited.
In order to use ISAM, apart from enabling the relevant code in run_cctm.csh, certain settings must be added to specific documents such as setting
TAG NAME, REGION(S), and EMIS STREAM(S) in the isam_control.txt file. I understand that
TAG NAME can be user-defined within three characters, while the latter two should be set to the variable names included in GRIDMASK.nc and the label of different emission sources in run_cctm.csh. My question is, what is the maximum number of TAG NAMEs that can be added in one simulation? For instance, if I want to trace five regions and six emission sources simultaneously, I will need to add 30 sets of TAGs. Will it affect the simulation performance to some extent?
Furthermore, adjustments need to be made to ‘&RegionsRegistry’ content in EmissCtrl.nml. I noticed in the nml file that
For example, to refer to file “CMAQ_REGIONS” with path “/home/user/data/cmaq/cmaq_region_file.nc” the specification in the CMAQ runscript would look like: SETENV CMAQ_REGIONS /home/user/data/cmaq/cmaq_region_file.nc
Note that an unlimited number of files can be used here, but each must contain a path for reference in the runscript.
Does this mean that multiple File Labels can be set simultaneously or does it refer to
SETENV CMAQ_REGIONS /home/user/data/cmaq/cmaq_region_file.nc? If it refers to the latter, how can I set multiple files in the SETENV CMAQ_REGIONS code?
Regarding the ‘Variable on File’ in ‘&RegionsRegistry’ of EmissCtrl.nml, typically, I use ‘ALL’. However, if there are other variables in my GRIDMASK.nc besides the defined regions (but not mentioned and not used in the isam_control.txt), will it have any impact?
Thank you for taking the time to address my questions.