# CMAQV5.3 ISAM Region not found

**URL:** <https://forum.cmascenter.org/t/cmaqv5-3-isam-region-not-found/1418>\
**Category:** CMAQ\
**Created:** [April 7, 2020, 7:45pm UTC](https://forum.cmascenter.org/t/cmaqv5-3-isam-region-not-found/1418 "2020-04-07T19:45:21Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\
**Post date:** [April 10, 2020, 12:08am UTC](https://forum.cmascenter.org/t/cmaqv5-3-isam-region-not-found/1418/8 "2020-04-10T00:08:28Z")

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Hello Yukui,

in theory you can use ncl to generate a file that complies with I/O API standards and is readable by I/O API library functions, but it is not at all trivial and requires an in-depth understanding of the I/O API standards. While there may be some initial learning curve, you probably will find it easier to generate the file by creating Fortran code that utilizes I/O API library functions or by possibly working with existing I/O API M3tools programs that are part of I/O API. You may also find [this following discussion thread](https://forum.cmascenter.org/t/error-creating-gridmask/1254) of interest and might want to reach out to the user to see how they solved their problem.

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