# Create ICON file **URL:** \ **Category:** Run Time Errors and Issues\ **Created:** [November 21, 2021, 5:37pm UTC](https://forum.cmascenter.org/t/create-icon-file/2835 "2021-11-21T17:37:06Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Hanye](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Hanye](https://forum.cmascenter.org/u/Hanye)\ **Post date:** [November 21, 2021, 5:37pm UTC](https://forum.cmascenter.org/t/create-icon-file/2835/1 "2021-11-21T17:37:06Z")
Hi! I am trying to create an ICON file base on two ICON file with netCDF4 package in python. then I checked new ICON file in a test run, But there is an ERROR : “”""GR\_EM\_SYM\_DATE\_0 | F Error opening file at path-name: netCDF error number -51 processing file “INIT\_CONC\_1” NetCDF: Unknown file format NetCDF: Unknown file format /home/wrf-cmaq/CMAQ/data/Global\_Tehran/icon/ICON\_v532\_Tehran\_6km ``` *** ERROR ABORT in subroutine gridded_files_se on PE 000 Open failure for INIT_CONC_1 ``` PM3EXIT: date&time specified as 0 Date&time specified as 0""""" I checked the structure of new ICON file with other ICON files but it’s the same. I don’t know how to fix this ERROR and where is I am wrong?! you can download new ICON file and the LOG file (point\_down:) [CTM\_LOG\_000.v532\_gcc\_Tehran-6km\_20210124.txt](https://forum.cmascenter.org/uploads/short-url/9mekjDj2d4K2N7IVdwW1czZCGVC.txt) (9.1 KB) ICON file: [https://drive.google.com/file/d/1LmxW0GP26piwLuOMVVESCzzIbc42djKq/view?usp=sharing](https://drive.google.com/file/d/1LmxW0GP26piwLuOMVVESCzzIbc42djKq/view?usp=sharing) ---
**Author:** ![cjcoats](https://avatars.discourse-cdn.com/v4/letter/c/ac8455/32.png) [@cjcoats](https://forum.cmascenter.org/u/cjcoats)\ **Post date:** [November 21, 2021, 5:41pm UTC](https://forum.cmascenter.org/t/create-icon-file/2835/2 "2021-11-21T17:41:58Z")
See [https://cjcoats.github.io/ioapi/AVAIL.html#ncf4](https://cjcoats.github.io/ioapi/AVAIL.html#ncf4). There have been problems with netCDF not being compatible with itself, especially with Version 4. Make sure that your python package is creating “netCDF Classic” format. By the way, [The Models-3 I/O API is A programming interface, not a data format !! I/O API files are not synonymous with “netCDF files” !!](https://cjcoats.github.io/ioapi/index.html). Treating it as a data format (as you are doing with your python stuff) is **NOT SUPPORTED**. ---
**Author:** ![cgnolte](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.cmascenter.org/cgnolte/32/53_2.png) [@cgnolte](https://forum.cmascenter.org/u/cgnolte)\ **Post date:** [November 24, 2021, 4:06pm UTC](https://forum.cmascenter.org/t/create-icon-file/2835/3 "2021-11-24T16:06:03Z")
As Carlie notes above, the error you are seeing is likely from your python code writing files using a form of netCDF that is incompatible with the version compiled with your version of IOAPI. But even if you fix that issue, you will likely run into other problems. IOAPI is an interface, and you should use that interface to create the files. If you want to combine species from different existing ICON files (assuming they have the same time stamp and are on the same domain), then you can use EPA’s [combine](https://github.com/USEPA/CMAQ/tree/main/POST/combine) program, or one of the IOAPI [tools](https://www.cmascenter.org/ioapi/documentation/all_versions/html/AA.html#tools), perhaps m3combo. ---
**Author:** ![benettonb1](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@benettonb1](https://forum.cmascenter.org/u/benettonb1)\ **Post date:** [November 25, 2021, 9:00am UTC](https://forum.cmascenter.org/t/create-icon-file/2835/4 "2021-11-25T09:00:33Z")
thank you for your reply this is really helpful for me ---
**Author:** ![benettonb1](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@benettonb1](https://forum.cmascenter.org/u/benettonb1)\ **Post date:** [December 7, 2021, 8:44am UTC](https://forum.cmascenter.org/t/create-icon-file/2835/5 "2021-12-07T08:44:24Z")
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