# MEGAN32 Preprocessing Issues

**URL:** <https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188>\
**Category:** MEGAN\
**Created:** [April 28, 2026, 8:19am UTC](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188 "2026-04-28T08:19:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Tend](https://avatars.discourse-cdn.com/v4/letter/t/3be4f8/32.png) [@Tend](https://forum.cmascenter.org/u/Tend)\
**Post date:** [April 28, 2026, 8:19am UTC](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188/1 "2026-04-28T08:19:57Z")

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Hello, I am encountering some issues while attempting to calculate biogenic emissions using the online MEGAN module within CMAQ 5.4. I have successfully generated various CSV and NetCDF files—such as CT3\*, FERT\*, LANDTYPE\*, etc.—through MEGAN 3.2 preprocessing. While the spatial distributions of some of these files appear reasonable, the spatial distributions of the EFMAP.2019b._.ncf and LDF\__.2019b.ncf files—which are output via the OutputGridEF._.csv files—exhibit obvious errors. I have verified that the exact same domain settings were used for all preprocessing steps. The preceding file, grid\_growth\_form._.csv, can be largely confirmed to be without issues by comparing its values with those in the CT3.csv file. However, the presence of problems in the ecotype.csv file is uncertain, and it is also unknown whether MEGAN\_EFP.py generated OutputGridEF using errors.The simulated region is East Asia at a 36 km resolution; I am unsure whether this is related to the specific region. I would greatly appreciate any assistance you can provide in resolving this matter.

For example EFMAP.2019b.\*.ncf

 ![微信图片_20260428160516_71_199](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/a/a2cb67743760fa11de596527eee083339c07164b.png)

For exampleNDEP\_\*.ncf

 ![微信图片_20260428160623_72_199](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/5/5d5b3fe6f8ca6b4cfa21164d62035ece7e256519.png)

[megan\_error.tar.gz](https://forum.cmascenter.org/uploads/short-url/9mqAb2uGmMwXovB7otDXfc7Zih4.gz) (5.3 MB)

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**Author:** ![willison.jeff](https://avatars.discourse-cdn.com/v4/letter/w/c89c15/32.png) [@willison.jeff](https://forum.cmascenter.org/u/willison.jeff)\
**Post date:** [April 28, 2026, 12:30pm UTC](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188/2 "2026-04-28T12:30:07Z")

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Congratulations on getting this far. Can you share

> WRF file you’re using for the MEGAN preprocessor
> 
> prepmegan4cmaq.ecotype.inp
> 
> prepmegan4cmaq.growthform.inp
> 
> prepmegan4cmaq.cantype.inp

I’ll run it through my workflow and see if I can reproduce the issue.

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<div class="post-metadata">

**Author:** ![Tend](https://avatars.discourse-cdn.com/v4/letter/t/3be4f8/32.png) [@Tend](https://forum.cmascenter.org/u/Tend)\
**Post date:** [May 22, 2026, 6:23am UTC](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188/3 "2026-05-22T06:23:16Z")

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[megan3\_test.tar.gz](https://forum.cmascenter.org/uploads/short-url/b91se80LYyA8ycSEcsyeiLJViZz.gz) (5.7 MB)

I apologize for the delay in replying; I was held up by other matters recently. Due to file size limitations, I deleted some variables in wrfinput\_d01, which I believe do not affect the creation of the Megan file. If there are any problems, please let me know so I can re-upload. Thank you!