Error with WRF-Chem (chem_opt = 202) Simulation

Kamran Ansari

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Apr 10, 2026, 4:35:14 PMApr 10

to wrf-chem-run

Dear All,

I am getting the errors of "Program received signal SIGSEGV: Segmentation fault - invalid memory reference" and "ASTEM internal steps exceeded 1000" with multiple warning lines of "WARNING: Large total lw optical depth of Infinity at point i,j,nb= ..." when running WRF-Chem with chem_opt = 202 (MOZART-MOSAIC + aqueous chemistry).

I have attached the namelist.input, rsl.out, and rsl.error files. Error messages are detailed in rsl.error.0020 file.

I have attempted several troubleshooting steps, including modifying the simulation domain, spatial resolution, time step, ASTEM iterations, emission files, and even switching WRF versions (WRF v4.2.2, v4.5.2, and v4.7.1). However, the issue persists. Notably, the same emission files and configuration run successfully with chem_opt = 201 (MOZART-MOSAIC without aqueous chemistry).

I observed that if photdt > radt as provided in namelist.input, the model stops after photdt minutes; otherwise, it stops after radt minutes.

I kindly request to check the attached files and provide your feedback. I would greatly appreciate any suggestions or help anyone may have regarding this issue.

Thank you very much for your time and help.

Best Regards,
Kamran

rsl.error.0020

namelist.input

rsl.error.0000

rsl.out.0000

Mary Barth

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Apr 10, 2026, 4:48:46 PMApr 10

to Kamran Ansari, wrf-chem-run

Hello Kamran,

I need to get a few other things done before looking at your files, but I have a couple of quick comments.

chem_opt = 201 and 202 also differ in how they treat SOA production. Option 201 uses a simple scheme while 202 uses a VBS scheme.

If you want to rule out aqueous chemistry, then run chem_opt=202 but with cloudchem = 0 set in the namelist.

Have you looked at the Google group archived issues/questions? This error has been brought up before and those previous discussions may help you. Further, I have shared an example 202 namelist before. It's shared again here.

- Mary

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Mary Barth

Senior Scientist, NSF National Center for Atmospheric Research

phone: 303-497-8186 email: bar...@ucar.edu

Staff web page SIMA Web Site MUSICA Web Site

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namelist.input_toshare

Kamran Ansari

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Apr 24, 2026, 5:50:16 AM (12 days ago) Apr 24

to wrf-chem-run, Mary Barth

Hi Ma'am,

Thank you for your reply and for sharing the example 202 namelist file. I want to include the aqueous chemistry in chem_opt 202, so I have kept cldchem_onoff = 1. I checked the previous conversations in this group related to this error, but the suggested solutions did not resolve it in my case. If you could redirect to a specific solution, I would be happy to try it.

I cross-checked the provided example file with my namelist, but the model still encountered the same error even with the same configuration. I also checked my emission and input files, and they appear to be normal.

I think the error is related to large shortwave and longwave optical depths in the aqueous process after the 30-minute time step (equal to photdt and radt). This results in multiple warning lines of "Large total sw optical depth of..." and "Large total lw optical depth of..." in rsl.error.0000 and rsl.out.0000 files. I have attached the AOD plot at 0.55 um, where AOD values increase abruptly from reasonable values at 00:29:00 to very large values at 00:30:00. I would greatly appreciate it if you could please check the attached files and suggest possible solutions to resolve this issue.

Thank you for your time and help.

Best Regards,
Kamran

rsl.error.0066

AOD_high_error.jpg

rsl.out.0000

rsl.error.0000

namelist.input

Mary Barth

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Apr 27, 2026, 2:38:00 PM (9 days ago) Apr 27

to Kamran Ansari, wrf-chem-run

Hello Kamran,

Thanks for the update. If you do a test run with cldchem_onoff = 0, then you can confirm the cloud chemistry is causing the issue.

I noticed that the error occurred at 30 minutes, which makes me wonder if there are processes called once per 30 minutes. Perhaps one of those processes is causing the high AOD. -- photolysis? plumerise frequency?

You may want to check the wrffireemis files again. They can be hard to look at spatially, so check the maximum values.

Also, this error has come up before in this discussion forum, so please look at the archive for other suggestions.

I think there is a thread about biomass burning code that may need to be edited (depending on the WRF version you have) to not have the code look for (I think) DMS fire emissions.

Good luck,

Mary

^--^--^--^--^--^--^--^--^--^--^--^--^--^--^-^--^--^--^-^--^

Mary Barth

Senior Scientist, NSF National Center for Atmospheric Research

phone: 303-497-8186 email: bar...@ucar.edu

Staff web page SIMA Web Site MUSICA Web Site

^--^--^--^--^--^--^--^--^--^--^--^--^--^--^-^--^--^--^-^--^

Kamran Ansari

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Apr 29, 2026, 1:52:25 AM (7 days ago) Apr 29

to wrf-chem-run, Mary Barth, wrf-chem-run

Hi,

I performed a test run with cldchem_onoff = 0, but the same error persists.

The photolysis (photdt) and radiation physics (radt) are called every 30 minutes, and I think these processes are causing the high AOD. After adjusting these values, I observed that if photdt > radt, the model stops after photdt minutes; otherwise, it stops after radt minutes. I have adjusted the plumerisefire_frq, but the model still stops despite the change.

I checked the wrffirechemi files, and they appear to be normal, as they are generated with standard wrf2fire_map using FINNv2.5 via the fire_emis preprocessor. I observe the same error when using both FINNv1.5 and v2.5 emissions.

For the test run, I tried with biomass_burn_opt = 0 (no biomass burning emissions), emiss_opt = 0 (no anthropogenic emissions), and bio_emiss_opt = 0 (no biogenic emissions), but the error still occurs in all cases. It shows that emissions files are not causing this error; therefore, the issue seems to be related to photolysis and radiation physics processes. I would appreciate it if you could comment on this and suggest solutions to resolve this issue.

I checked the previous discussions in this group related to this error, but the suggested solutions did not resolve it. If you could redirect to a specific solution, I would be happy to try it.

Thank you for your time and help.

Kasapeco Ltd

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May 1, 2026, 4:14:49 AM (5 days ago) May 1

to wrf-chem-run, Kamran Ansari, Mary Barth, wrf-chem-run

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