# CMAQ error at AQCHEM

**URL:** https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499
**Category:** Run Time Errors and Issues
**Created:** [January 29, 2019, 6:32pm UTC](https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499 "2019-01-29T18:32:09Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![ehsan](https://avatars.discourse-cdn.com/v4/letter/e/96bed5/32.png) [@ehsan](https://forum.cmascenter.org/u/ehsan)
#### Post date: [January 29, 2019, 6:32pm UTC](https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499/1 "2019-01-29T18:32:09Z")

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Hello,

I am getting the following error while running CMAQv521. I am running for whole September of 2016 and CMAQ crashed on 13th.  
Does anyone have any idea why I am getting this error?  
I am running CMAQ with modified IC and BC files to values 1E-10 to minimize the influence of BC conditions.

Thanks.

```
 *** ERROR ABORT in subroutine AQCHEM on PE 091          
 Maximum AQCHEM total iterations exceeded

```

 ![46%20AM](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/1X/f301e36c36fb89a8fe2655082c6a1dcbd3191eaa.jpeg)

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### 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: [January 31, 2019, 7:19pm UTC](https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499/2 "2019-01-31T19:19:30Z")

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When I have had this error, it has always been a result of something going wrong elsewhere in the model or its input data, such that tweaking the AQCHEM convergence criteria or number of allowable iterations was not the right way to go. Most recently, this happened to me when I had bad (unreasonably large) precipitation values in the METCRO2D file.

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### Author: ![Aurora](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Aurora](https://forum.cmascenter.org/u/Aurora)
#### Post date: [December 6, 2021, 3:45pm UTC](https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499/3 "2021-12-06T15:45:49Z")

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> [@cgnolte](#):
>
> 当我在METCRO2D文件中有不好（不合理的大）降水值

How did you solve this problem? I also have this problem. First, I checked the emiss file, but I didn’t find a negative value. I don’t know what else I need to check. You said there was a problem with METCRO2D. Does that mean there may also be a problem with the MCIP module?

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### 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: [December 6, 2021, 3:55pm UTC](https://forum.cmascenter.org/t/cmaq-error-at-aqchem/499/4 "2021-12-06T15:55:44Z")

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> [@cgnolte](#):
>
> 当我在METCRO2D文件中有不好（不合理的大）降水值

WRF uses continuous “accumulated precipitation” variables RAINC and RAINNC, in mm. CMAQ requires precipitation during the time step (typically 1 hour). MCIP performs this calculation. The version of MCIP I was using at that time had a bug in the way it handled WRF’s “tipping bucket”. As a result, the MCIP output indicated that over 1 meter of rain fell in a single hour. This led to AQCHEM taking too small of an internal time step, with the result that it did not converge in the allotted number of iterations.

Check your MCIP precipitation variables. Are there any unreasonably large (over 1 meter) values?  
If so, rerun using an updated version of MCIP – this bug was corrected years ago.

If not, please read the “READ ME FIRST: getting started” post, then post your message in a new thread.