KPP failed to converge after 2 iterations!

[1392403848]

Your name

czr

Your affiliation

Tsinghua University

What happened? What did you expect to happen?

Hi！ I want to simulate the concentration of SO3. I have followed the official website's procedure to add the corresponding substances to GEOS-Chem and successfully compiled it. However, when checking the log, an error occurred indicating that the results did not converge after two iterations. I'm not sure where the mistake is. Is it because the rate of SO3 turning into H2SO4 is too fast, causing the non-convergence? If this is the reason for the non-convergence, how can I change it to get the concentration of SO3? Thank you.

What are the steps to reproduce the bug?

I haven't made any other attempts yet because I'm not sure where to start looking. This issue has been bothering me for several days, and the constant errors are really frustrating. If you could help me compile and see what's going wrong, that would be great.

Please attach any relevant configuration and log files.

geoschem_config.txt GC.log HISTORY.txt custom.eqn.txt species_database.txt

What GEOS-Chem version were you using?

14.3.1

What environment were you running GEOS-Chem on?

Personal computer

What compiler and version were you using?

gcc 9.3.0

Will you be addressing this bug yourself?

No

In what configuration were you running GEOS-Chem?

GCClassic

What simulation were you running?

Full chemistry

As what resolution were you running GEOS-Chem?

4*5

What meterology fields did you use?

MERRA-2

Additional information

No response

[yantosca]

Thanks for writing @1392403848, Could you provide some more detail about which reactions you added to the custom.kpp file? It's hard to tell from just looking at the file itself.

Looking at your log file there are a lot of negative species concentrations. I would start by trying to isolate where the negatives are coming in. Try turning off transport, wet deposition, convection and then turning them back on one at a time in successive runs.

We have some suggestions that try on our ReadTheDocs. See:

• https://geos-chem.readthedocs.io/en/latest/geos-chem-shared-docs/supplemental-guides/error-guide.html#forced-exit-from-rosenbrock

This type of issue can sometimes be hard to debug. Several other users have reported similar issues, see the link below for details. Perhaps you can try one of the suggestions made in these issues.

• https://github.com/geoschem/geos-chem/issues?q=is%3Aissue+label%3A%22topic%3A+Chemical+Mechanisms%22+converge+is%3Aclosed

BTW, I also noticed you have a typo in your species_database.yml file:

HSO5:
Formula: HSO5
  FullName: HSO5
  Is_Gas: true
  MW_g: 113.07

the Formula: HSO5 should be indented 2 spaces so that it comes under the HSO5 species. This might not be a fatal error but should be corrected anyway.

Keep us posted!

[1392403848]

Hi！ I haven't modified the custom.kpp file and didn't add any new species. Instead, I added reactions and rate constants for SO3 in the custom.eqn file.But I've still attached the custom.kpp file for your reference. custom.kpp.txt Here are the reactions I added in the custom.eqn file：

Initially, I thought the issue was that the production rate of SO3 was much slower than its consumption rate, leading to non-convergence. However, even after increasing the production rate of SO3, I encountered the same error.I have changed the reaction rate for the formation of SO3 from SO2 to 1.3d-8. I'm not sure what the cause is.I have also attached the custom.eqn file. custom.eqn.txt

Thank you for your suggestion regarding HSO5, which I find very useful!

[yantosca]

Thanks @1392403848 for the feedback. I see the new species in the custom.eqn file. Just checking, did you also make entries for these in the species_database.yml file?

HO2_H2O    = IGNORE; {HO2 + H2O}
SO3        = IGNORE; {SO3}
HSO5       = IGNORE; {HSO5}
H2O_H2O    = IGNORE; {H2O_H2O}

If you could help me compile and see what's going wrong, that would be great.

Unfortunately we do not have the resources to debug non-standard chemistry mechanisms. But we can try to give you helpful advice so that you can try to isolate the problem yourself.

I would start by trying to figure out why you are getting several negative species. Does that happen before chemistry, or during chemistry? That may give you some ideas as to what to look into.

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