I am not sure when will DESID grid making be released?
“Tutorials demonstrating a process for creating custom region variables for any grid using open-source tools will be available in future CMAQ repositories”
Should I match the grid size for running CMAQ?
e.g. If I use 4km x 4km grid and want to modify emission MA area, Can I use 12km x 12km grid files?
Because I can download CMAQ grid mask files for 12km CONUS (ISAM) from EPA warehouse.
To my knowledge, there currently is no planned release date for such tutorials, but I could be wrong.
Yes, your grid mask file needs to match your modeling domain. You cannot use the 12 km grid mask file from the data warehouse to manipulate emission streams for a 4 km modeling domain.
Is there any other way to know how to make grid to use DESID region option?
There are at least two aspects to this process:
create a gridded file in any format representing the geographical features in your domain (states, counties, regular shaped boxes, etc.) which you would like to reference in DESID
Create an I/O API file containing one REAL variable of fractions between 0 and 1 for each such feature.
There is no ready-made tool for the first step fitting all situations. Depending on their problem, people have used the Spatial Allocator, written custom Fortran code to read information from SMOKE gridding surrogates for their domain and generate gridded files (see the description in the README file for the 12 km grid mask files we posted to the CMAS data warehouse), or used GIS tools to manipulate shapefiles.
For the second step, a number of people have used a combination of tools
m3merge. For examples, see the discussion in these threads:
What’s the maskdata’s format?
ISAM SA_ACONC output error
How to make ISAM_REGIONS file?