M3tool (m3combo)

I/O API m3tools
1

Hello.
I am trying to subtract two files with all variables (A and B)
But I do not know how to subtract all variables.
I was able to subtract single variable (NO2 as test)
https://www.cmascenter.org/ioapi/documentation/all_versions/html/M3COMBO.html
Is there any other way to subtract two files, leaving their own units?

NO2
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ALL
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error
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2

m3tools program m3diff might be what you’re looking for. It can create a gridded output file of the differences between two input files, in addition to creating a text-based REPORT file with a summary of the differences.

4

How can I create gridded output file?
I was only able to get report file.

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5

Before running m3diff and entering logical file name ‘TEST’ as the gridded output file, did you do
setenv TEST /path/to/some/output_file.nc, or were you just trying to create a file TEST right in the directory where you were running m3diff? The latter should be fine, though I always prefer to use setenv to associate the logical file names with actual file names.

Frankly, I’m not quite sure what is happening here.

What does the screen output right after the line Enter logical name for OUTPUT file [OFILE] >> TEST show? If somehow there was a problem opening the file (e.g. because of an invalid path, or missing write permissions), there should have been some error message, and the program should have just reprompted you for a valid entry. On the other hand, if the file was successfully opened, it should have shown something like this

Enter logical name for OUTPUT FILE [OFILE] >>TEST3

 "TEST3" opened as UNKNOWN(R-W)
 File name "TEST3"
 File type GRDDED3

and for each time step and variable being processed, the screen output should have looked something like this, including the message that values were being written to TEST3.

Date and time  2017274:000000 (0:00:00   Oct. 1, 2017)
  A:AFILE/NO2  vs  B:BFILE/NO2  vs  (A - B)
     Max  @ (c,r,l)           Min  @ (c,r,l)          Mean         Sigma
     A    4.31343E-02@( 99,154,  1)  2.50794E-08@( 94, 85,  1)  5.62475E-04  1.63840E-03
     B    4.31343E-02@( 99,154,  1)  2.50793E-08@( 94, 85,  1)  5.62475E-04  1.63840E-03
     Value for IOAPI_LOG_WRITE not defined;returning default:   TRUE
     NO2 written to TEST3 for   2017274:000000
    A:B  2.90293E-06@( 65,141,  1) -1.08103E-06@(183,106,  1) -2.60368E-11  1.98708E-08
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