# Combine run issue

**URL:** <https://forum.cmascenter.org/t/combine-run-issue/450>\
**Category:** Post-processing\
**Created:** [December 17, 2018, 7:59pm UTC](https://forum.cmascenter.org/t/combine-run-issue/450 "2018-12-17T19:59:00Z")\
**Posts on this page:** 1\
**Showing post:** 18

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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:** [June 11, 2022, 12:48am UTC](https://forum.cmascenter.org/t/combine-run-issue/450/18 "2022-06-11T00:48:48Z")

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I’m guessing from the name of your directory path (“EMAQ1p3km”) that your grid resolution is 1.3333 km and that there may be very slight differences in the XCELL and/or YCELL attributes between the CCTM\_ACONC file opened as INFILE1 and the METCRO3D files opened as INFILE2. You could verify this by doing an ncdump -h on both files and comparing the grid attributes.

There is a known shortcoming of the portion of `combine` that ensures consistency of grids across files before combining variables from the different files. This shortcoming affects domains with “odd” grid spacing and/or grid origin values. There are multiple examples of this issue in [this thread](https://forum.cmascenter.org/t/error-in-running-combine-for-cmaq5-3-1/2165/13), along with suggested code changes to solve this issue by relaxing the tolerance criteria or making these criteria relative rather than absolute (the more robust solution).

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_[View the full topic](https://forum.cmascenter.org/t/combine-run-issue/450)._