CVMix and Stokes drift modules

[qingli411]

This PR adds two modules to GOTM:

• CVMix
• Stokes drift

The CVMix module is enabled by building GOTM with the CMake flag -DGOTM_USE_CVMIX=true and using turb_method=100. It includes an interface (do_cvmix separate from do_turbulence) to call CVMix subroutines to do KPP (Large et al., 1994) and a few variants that include the effects of Langmuir turbulence (Li et al., 2016 and Li and Fox-Kemper, 2017). The CVMix library is included as a submodule.

The Stokes drift module provides a way to include the Stokes drift information in GOTM for use in ocean surface boundary layer turbulence closure schemes. It is enabled by default with zero Stokes drift. It introduces the following variables:

• Stokes drift profiles in x- and y-directions (usprof, vsprof), with input options
  • Read from a file
  • Compute from the surface value and a decay scale assuming exponential profile
  • Compute from the wind using the 'theory-wave' option of Li et al., 2017
• Stokes drift shear profiles in x- and y-directions (dusdz, dvsdz), with input options
  • Read from a file
  • Compute from the Stokes drift profile
• Surface value of the Stokes drift in x- and y-directions (us0, vs0) and a decay scale (ds), with input options
  • Constant
  • Read from a file
• A few variants of the turbulent Langmuir number introduced by McWilliams et al., 1997, Harcourt and D'Asaro, 2008, Van Roekel et al., 2012 and Reichl et al., 2016
• A few variants of the Langmuir enhancement factor introduced by Li et al., 2016 and Reichl et al., 2016

[qingli411]

Please don't merge yet. Still need a few more tests. Also the CVMix submodule is pointing to a branch in my CVMix repository that has CMake support (see da0a951). Will point to the CVMix repository once the CMake changes are merged to CVMix.

[bolding]

Hi Qing

Thanks for the PR. I'll wait with merging until you give the green light - and also considering other comments (if any :-))

I've send a mail to the GOTM mailings lists - so lets see if there is any activity.

Karsten

[hburchard]

Hi Qing,

thanks a lot for the well-structured documentation. Which are the test cases you want to test? The ones that I would recommend are gotland (Central Baltic Sea), nns_seasonal (Nothern North Sea), and OWS Papa. Let me know, in case that some of them do not work for you.

Cheers, Hans.

[lumlauf]

Hi all,

I would also suggest that we have 1-2 idealized test cases. Perhaps we could build up on our classical "entrainment" test case to see how LC modifies mixed layer entrainment in a simple, idealized environment.

Cheers,

Lars

Am 2020-06-10 um 12:46 schrieb hburchard:

Hi Qing,

thanks a lot for the well-structured documentation. Which are the test cases you want to test? The ones that I would recommend are gotland (Central Baltic Sea), nns_seasonal (Nothern North Sea), and OWS Papa. Let me know, in case that some of them do not work for you.

Cheers, Hans.

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--

Lars Umlauf

Physical Oceanography and Instrumentation Leibniz-Institute for Baltic Sea Research

phone : ++49 381 5197 223 fax : ++49 381 5197 114 web : www.io-warnemuende.de/lars-umlauf-en.html

address: Leibniz-Institute for Baltic Sea Research Seestrasse 15 D-18119 Rostock-Warnemuende Germany

[qingli411]

I have quickly tried the Gotland and FLEX cases using the new code and they work and the results look reasonable. I think we want a few tests to make sure:

• Adding the two modules don't change answers of the existing test cases if using the same setup, for which I think we can just use the Gotland and FLEX cases.
• CVMix is working properly with and without Langmuir turbulence parameterization, for which I'm planning to compare with my test cases in Li et al, 2019.

I think a simple and classical entrainment test case is a good idea. I have similar entrainment test cases in Li et al, 2019 to compare with LES. I think I will try to reproduce Fig. 15 of that paper using the new code.

One question I have:

• Currently the bottom layer subroutine in the CVMix module is still empty. I wonder whether we need to implement that? To me it makes more sense and is simpler to just remove it as I don't expect people to use CVMix in a shallow water environment. There are many issues, for example, there is not a good way to deal with overlapping surface and bottom boundary layer in CVMix... What do you think?

[hburchard]

Qing, I would propose that for the first we leave out the bottom boundary layer in cvmix. There are so many pitfalls and it would mean quite some more development and testing. In a later stage, someone could include this.

Cheers, Hans.

[lumlauf]

I agree with Hans. It is not a big step to include the bottom module because we can recycle most of the routines from the SML module. But let's wait with this until somebody really needs it.

Best,

Lars

Am 2020-06-12 um 17:35 schrieb hburchard:

Qing, I would propose that for the first we leave out the bottom boundary layer in cvmix. There are so many pitfalls and it would mean quite some more development and testing. In a later stage, someone could include this.

Cheers, Hans.

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--

Lars Umlauf

Physical Oceanography and Instrumentation Leibniz-Institute for Baltic Sea Research

phone : ++49 381 5197 223 fax : ++49 381 5197 114 web : www.io-warnemuende.de/lars-umlauf-en.html

address: Leibniz-Institute for Baltic Sea Research Seestrasse 15 D-18119 Rostock-Warnemuende Germany

[qingli411]

Sounds good. I will push a commit to clean that up.

[qingli411]

Here are some updates.

• I have run the Gotland and FLEX cases using GLS in this branch and compared them with the master branch and the results are identical, which is expected as no change is made in that part. CVMix also runs in the Gotland and FLEX cases, results are slightly different from GLS but reasonable.
• I have tested the CVMix and Stokes drift modules using some of my test cases in Li et al., 2019.
  1. OSMOSIS winter (see the notebook here).
  2. OSMOSIS spring (see the notebook here).
  3. A set of idealized mixed layer entrainment cases under different surface forcing conditions (see the notebook here).

I think it is ready to be merged except that the CVMix submodule is still pointing to my CVMix fork. Please let me know if there is anything else that need to be changed in this branch.

[bolding]

Hi Qing

The old thing missing is then the update of the official CVMix repository before we can merge.

Karsten

[qingli411]

Now CVMix is pointing to the main CVMix repository.