Add new dust emission scheme

[L3atm]

We propose to add a new dust emission scheme improving the dust mobilization parameterizations in CESM2. We also propose to add a namelist entry and switches in the code, such that CESM2 users could turn on and off this new dust emission scheme easily. These will imply changes in the following files:

• clm/src/biogeochem/DUSTMod.F90

• cam/src/chemistry/modal_aero/dust_model.F90

• clm/src/main/clm_varctl.F90

• clm/src/main/controlMod.F90

• cam/bld/build-namelist

• cam/bld/namelist_files/namelist_definition.xml

• clm/bld/namelist_files/namelist_definition_clm4_5.xml

• clm/bld/namelist_files/namelist_definition_clm4_0.xml

• user_nl_cam

• user_nl_clm

Brief science information:
The physically-based new dust emission scheme produces a statistically significant improvement in the representation of dust emission compared to the default scheme used in the current CESM2. This new dust emission scheme also reduces the need to use an empirical source function in the dust cycle simulation to shift emissions toward the word's most erodible regions.

Pseudocode for all file changes:

• clm/src/biogeochem/DUSTMod.F90: implementing the new dust mobilization parameterization due to wind from the surface into the lowest atmospheric layer

• cam/src/chemistry/modal_aero/dust_model.F90: turning off the soil erodibility map used by the default old scheme

• clm/src/main/clm_varctl.F90: adding a switch to turn on and off the new dust emission scheme

• clm/src/main/controlMod.F90 plus clm/bld/namelist_files/namelist_definition_clm4_5.xml and namelist_definition_clm4_0.xml along with cam/bld/build-namelist: adding a flag to read the new namelist entry

• user_nl_cam and user_nl_clm: setting the new namelist entry by the users to use the new scheme for simulation

Long term goal:
To add the suggested feature to the master branch of CESM2.

[wwieder]

@L3atm thanks for filing this issue and letting is know about this plan. We look forward to hearing more about your work. Out of curiosity, who are you & where do you work? It's helpful on our end to be able to talk about the people who are making the science of CTSM happen.

[L3atm]

@wwieder Hi! Nice to meet you here. This is Longlei Li, a postdoc working with Natalie Mahowald at Cornell. We look forward to working with you on this too.

[wwieder]

awesome. Thanks Longlei. Good to meet you too. How mature is this work? Do you see yourself submitting a pull request soon, or is it just getting started? Regardless, keep us up to date on your progress. Best, Will

…

On Wed, Dec 16, 2020 at 7:31 AM L3atm ***@***.***> wrote: @wwieder <https://github.com/wwieder> Hi! Nice to meet you here. This is Longlei Li, a postdoc working with Natalie Mahowald at Cornell. We look forward to working with you on this too. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1230 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AB5IWJCZL6WJHDNZZI6HQR3SVDAC5ANCNFSM4U5MDIQQ> .

[L3atm]

Hi Will!
Thanks for the question. I think I will submit a pull request soon, and will keep you up to date!
Best regards, Longlei

[wwieder]

Hello, any updates on this issue? Is it still an active project?

[lkemmons]

Longlei @L3atm and Will @wwieder,
It would be helpful to coordinate this development with the implementation of MAM5 that Francis @fvitt is working on in ESCOMP/CAM#445
It would be good to create a new compset with the new dust emissions and MAM5, and not work on tuning each of these separately.

[wwieder]

I think this makes sense. @ekluzek typically makes compsets for CTSM. Erik is there anyone else on the land side that should be involved in this conversation?

It would help me to know about the timing of when the new dust scheme will be ready, when MAM5 will be ready, and when you'd like the compset @lkemmons ? My Friday most weeks is relatively open and my calendar is up to date if you want to try and schedule something.

[wwieder]

I'm also imagining that the modifications @L3atm started making in 2020 will need to be brought up to a current CTSM tag before we can merge. I don't expect too many conflicts with this, but wanted to highlight this priority may be needed before making a compset?

[lkemmons]

I think we need to hear from Longlei about the status of the dust. Francis has the MAM5 code and may be able to work on it soon. A compset would be made after both those steps. We think it would be valuable to have the compset for use in testing in the "workhorse" model development, but no specific deadline.

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On Wed, Oct 27, 2021 at 5:33 PM will wieder ***@***.***> wrote: I'm also imagining that the modifications @L3atm <https://github.com/L3atm> started making in 2020 will need to be brought up to a current CTSM tag before we can merge. I don't expect too many conflicts with this, but wanted to highlight this priority may be needed before making a compset? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1230 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AH5BH7M7HOEXZH3ORLWQ7XTUJCD4RANCNFSM4U5MDIQQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[L3atm]

Hello! What Louisa proposed makes sense to me too. The current modifications I have made are in CTSM part only. Modifications to CAM are also required and have not yet been done. We may need to coordinate with the CAM chemistry group on how to get those modifications into CAM. I will create a branch next in CAM soon. As a side note, we have recently revised the threshold soil moisture calculation in the land model in order to turn the soil moisture effect on. This change will be included here too.

[lkemmons]

It sounds like the dust code needs to be moved to current CTSM code. Who will be able to do that? Francis will be putting the MAM5 code into current CAM code soon. Would it be helpful to meet to discuss the next steps?

…

On Thu, Oct 28, 2021 at 9:12 AM Longlei Li ***@***.***> wrote: Hello! What Louisa proposed makes sense to me too. The current modifications I have made are in CTSM part only. Modifications to CAM are also required and have not yet been done. We may need to coordinate with the CAM chemistry group on how to get those modifications into CAM. I will create a branch next in CAM soon. As a side note, we have recently revised the threshold soil moisture calculation in the land model in order to turn the soil moisture effect on. This change will be included here too. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1230 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AH5BH7LHB5XXVK5J35U75V3UJFR6XANCNFSM4U5MDIQQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[ekluzek]

@lkemmons yes it sounds like we need to get the group together to talk about how to move forward with this. @wwieder should be part of the discussion so he can talk about who can work on it here in CESM. Can you propose a meeting?

[wwieder]

From our call today:

• @ekluzek suggested it would be best to start with a CTSM pull request so there's a CTSM tag that CAM can point to.
• @L3atm has all these code mods made and will point to the branch he's working on.
• @L3atm will open a pull request ASAP so he can work with @ekluzek
• @fvitt will work to bring in the CAM, but these changes are relatively modest
• @fvitt noted that since this will be answer changing for CAM it will need to be validated by AMP
• @lkemmons suggested that tuning for climate runs take place after additional CAM-CHEM modifications with MAM5 come into CESM.

We decided NOT to maintain backwards compatibility with the old dust scheme, which will be available in CESM2.1. Natalie said this new dust scheme is much better and should just replace the old (dated) dust scheme for CESM2.3 and beyond.

[lkemmons]

The CAM climate tuning can be done with the new dust scheme and MAM5 (5-mode Modal Aerosol Model), which will have a different coarse mode size for dust than MAM4.

[ekluzek]

I'm closing this because we decided to go with #1604 which is based on this work, but adds some additional improvements to it. We also decided we didn't need to support this solution in addition to it.