# Error reading IDs in CMAQ emission file

**URL:** <https://forum.cmascenter.org/t/error-reading-ids-in-cmaq-emission-file/3193>\
**Category:** Run Time Errors and Issues\
**Tags:** cmaq\
**Created:** [April 19, 2022, 4:42pm UTC](https://forum.cmascenter.org/t/error-reading-ids-in-cmaq-emission-file/3193 "2022-04-19T16:42:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jsm2093](https://avatars.discourse-cdn.com/v4/letter/j/b4bc9f/32.png) [@jsm2093](https://forum.cmascenter.org/u/jsm2093)\
**Post date:** [April 19, 2022, 4:42pm UTC](https://forum.cmascenter.org/t/error-reading-ids-in-cmaq-emission-file/3193/1 "2022-04-19T16:42:01Z")

</div>

Dear @fsidi,

I read a github post from you talking about the error “Error reading IDs”. I’m dealing with this error with an emission file that I’m customizing by changing the chemical mechanism (saprc07tc\_ae6). I know that in VAR-LIST from global attributes, all the variables must be exactly 16 characters long. However, I’m getting this error but I don’t know why if my VAR-LIST looks good. Can you help me with this?

This is the error that I’m getting:

```auto
"MET_DOT_3D" opened as OLD:READ-ONLY
     File name "/home/monteajs/CMAQ_intel/saprc07/data/mcipchem_ME_3km-v4/METDOT3D_210326.nc"
     File type GRDDED3
     Execution ID "mcip"
     Grid name "2020_test_DOT"
     Dimensions: 98 rows, 98 cols, 34 lays, 6 vbles
     NetCDF ID: 393216 opened as READONLY
     Starting date and time 2021085:000000 (0:00:00 March 26, 2021)
     Timestep 010000 (1:00:00 hh:mm:ss)
     Maximum current record number 25
     Error reading IDs for variable ????????????????
     netCDF error number -49 processing file "GR_EMIS_001"
     NetCDF: Variable not found

     *** ERROR ABORT in subroutine gridded_files_se on PE 017
     Could not open GR_EMIS_001 file
 PM3EXIT: date&time specified as 0
     Date&time specified as 0

```

And here is how looks my global attributes:

 ![Screenshot from 2022-04-19 19-40-22](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/a/a3f8b99a1f334573b9208d84cc75e7c10e8a6ea2.png)

```auto

// global attributes:
		:IOAPI_VERSION = "$Id: @(#) ioapi library version 3.2 $" ;
		:EXEC_ID = "WRFCHEM emissions converted to CMAQ and speciated to saprc07tc_ae6" ;
		:FTYPE = 1 ;
		:CDATE = 2022094 ;
		:CTIME = 131038 ;
		:WDATE = 2022094 ;
		:WTIME = 131038 ;
		:SDATE = 2021085 ;
		:STIME = 0 ;
		:TSTEP = 10000 ;
		:NTHIK = 1 ;
		:NCOLS = 97 ;
		:NROWS = 97 ;
		:NLAYS = 1 ;
		:NVARS = 81 ;
		:GDTYP = 2 ;
		:P_ALP = 22.3090000152588 ;
		:P_BET = 22.3090000152588 ;
		:P_GAM = 39.1049995422363 ;
		:XCENT = 39.1049995422363 ;
		:YCENT = 22.3089904785156 ;
		:XORIG = -145500. ;
		:YORIG = -145500. ;
		:XCELL = 3000. ;
		:YCELL = 3000. ;
		:VGTYP = -1 ;
		:VGTOP = 0. ;
		:VGLVLS = 0., 0. ;
		:GDNAM = "2020_test_CROSS " ;
		:UPNAM = "OUTCM3IO " ;
		:VAR-LIST = "AACD ACET ACETONE ACRO ACROLEIN ACYE ALK1 ALK2 ALK3 ALK4 ALK5 APIN ARO1 ARO2MN B124 BACL BALD BDE13 BENZ CCHO CCOOH CL2 CO CRES ETHE ETHENE ETOH FACD GLY HCHO HCL HCOOH HONO IPRD ISOP ISOPRENE MACR MEK MEOH MGLY MVK MXYL NAPHTHALENE NH3 NO NO2 OLE1 OLE2 OXYL PACD PAL PCA PCL PEC PFE PH2O PK PMC PMG PMN PMOTHR PNA PNCOM PNH4 PNO3 POC PRD2 PROPENE PRPE PSI PSO4 PTI PXYL RCHO RNO3 SO2 SOAALK SULF TERP TOLU " ;
		:FILEDESC = "Emissions used on WRFCHEM (wrfchemi_d01) and converted to CMAQ format" ;
		:HISTORY = "" ;
}

```

I don’t know why is reading an empty string of 16 characters if my global attributes seems to be fine.

Thanks.

---

<div class="post-metadata">

**Author:** ![fsidi](https://avatars.discourse-cdn.com/v4/letter/f/7feea3/32.png) [@fsidi](https://forum.cmascenter.org/u/fsidi)\
**Post date:** [April 19, 2022, 5:12pm UTC](https://forum.cmascenter.org/t/error-reading-ids-in-cmaq-emission-file/3193/2 "2022-04-19T17:12:24Z")

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@jsm2093, It’s a bit tough to debug your problem without having the actual file in front of me. A couple of things to note:

1. I/O API isn’t a data format it’s an programming interface. **So, in general DO NOT try to fake or build I/O API style files.** Either use I/O API to build these files from raw output OR use the approved python tools such as [The BAMS/EDSS/Models-3 I/O&nbsp;API](https://www.cmascenter.org/ioapi/documentation/all_versions/html/AA.html#python) to build these files. If you require help using I/O API please tag @cjcoats for help.

2. Your VAR-LIST doesn’t seem to match your variables. For example, your file has variable “SESQ” but your VAR-LIST doesn’t, miss-matches like this will cause I/O related errors like you are seeing. So cross reference your VAR-LIST with the actual variables in your file.