Unexpectedly high surface Br, BrO concentrations in v14.3

[emroy00]

Your name

Eric Roy

Your affiliation

MIT

What happened? What did you expect to happen?

Following discussion during last year's GEOS-Chem meeting, @arifein, @viral211 and I used output from the v14.3 of the full chem simulation to make new oxidant/aerosol fields which I have used to drive Hg simulations. v14.3 includes the mechanistic sea salt debromination scheme originally described in Zhu et al. (2019) as the default.

We find that Br and BrO concentrations are far higher than what was used in Shah et al. (2021) and the spatial distribution of BrO is inconsistent with that shown in Wang et al. (2021) (see attached presentation). According to the readthedocs page, mechanistic sea salt debromination became optional shortly after it was introduced in v13.4 due to its effect on ozone concentrations, but was reintroduced as the default in v14.2 after some chemistry updates were made. Is there any documentation/validation of the affects of these updates on surface Br/BrO loadings?

Thanks in advance!

Presentation:
Bromine_v14p3.pptx

Papers:
Zhu et al., (2019): https://doi.org/10.5194/acp-19-6497-2019
Wang et al., (2021): https://doi.org/10.5194/acp-21-13973-2021
Shah et al., (2021): https://doi.org/10.1021/acs.est.1c03160

What are the steps to reproduce the bug?

N/A

Please attach any relevant configuration and log files.

No response

What GEOS-Chem version were you using?

14.3.1

What environment were you running GEOS-Chem on?

Local cluster

What compiler and version were you using?

gcc 6.3.1 ...

Will you be addressing this bug yourself?

Yes

In what configuration were you running GEOS-Chem?

GCClassic

What simulation were you running?

Full chemistry

As what resolution were you running GEOS-Chem?

2x2.5

What meterology fields did you use?

MERRA-2

Additional information

No response

[yantosca]

Thanks @emroy00 for reaching out. I am not aware of documentation on the effect of seasalt debromination on Br/BrO, other than what we saw in our 1-year benchmarks for 14.2.0. We noted on the GEOS-Chem 14.2.0 wiki page:

Turn SSA debromination on by default

This updates adds back the BrSALA and BrSALC emission sources. It also impacts other emissions over oceans (iodine, PARANOX). Bromine species increase considerably over oceans and ozone decreases by up to 10 ppb over the Southern Ocean. Global mean OH changes by -1.23%.

I am tagging the Aerosols WG and Chemistry WG co-chairs as this is a science question.

• Tagging Aerosol WG co-chairs: @beckyalexander @theloniuspunk @wporte@emroy00
• Tagging Chemistry WG co-chairs: @barronh @luhu0 @jhaskinsPhD @kelvinhb

Also tagging @msulprizio