ctsm5.1.dev137

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Tag name: ctsm5.1.dev137
Originator(s): Ronny Meier, slevis (Samuel Levis,UCAR/TSS,303-665-1310)
Date: Tue Aug 22 14:34:53 MDT 2023
One-line Summary: Surface roughness modifications

Purpose and description of changes
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Surface roughness (z0) modifications that appear in this publication:
https://doi.org/10.5194/gmd-15-2365-2022

When changing the namelist input z0param_method from ZengWang2007 (default)
to Meier2022 the following modifications are activated:

- A new parameterization of the vegetation surface roughness based on
Raupach (1992) with optimized parameters to match the data collected in
Hu et al. (2020) for different types of vegetation. This requires several new
PFT-specific input parameters in the parameter file.
- A spatially explicit z0m input field for bare soil based on the data of
Prigent et al. (2005). This may be activated specifically by the user through
the namelist input use_z0mg_2d. This requires a new input variable in the
fsurdat file.
- The parameterization of z0m for snow based on accumulated snow melt as
proposed in Brock et al. (2006). This may be activated specifically by the
user through the namelist input use_z0m_snowmelt.
- The parameterization of Yang et al. (2008) for z0h and z0q over bare soil,
snow, and glaciers.
- The study in GMD also proposes new globally constant values for the
z0m of bare soil, snow, and ice. To "activate" those the parameter file needs
to be changed at the moment. The original and modified parameter files and
fsurdat files will be shared by ftp.

Open issues/questions (discussed with @ekluzek, @dlawrenncar, @olyson):

- How to incorporate the data of Prigent et al. (2005) in the surfdata
generation. I will write an email about this to Catherine Prigent.
- One statement marked in CanopyFluxesMod should probably be changed when
using Meier2022 (i.e., Yang et al. (2008) formulation should be used instead
of Zeng and Dickinson (1998)).
- At the moment one needs to change the parameter file to switch between the
original and proposed globally constant z0m values for bare soil, snow, and
ice. This is obviously not very user friendly and prone to mistakes.
- The introduction of Yang et al. (2008) frequently results in z0h and z0q
larger than z0m. This is only rarely observed in the field and in contradiction
to the theory that z0h and z0q should be smaller because heat and water vapor
need to be transported through molecular diffusion in the surface sublayer.


Significant changes to scientifically-supported configurations
--------------------------------------------------------------

Does this tag change answers significantly for any of the following physics configurations?
(Details of any changes will be given in the "Answer changes" section below.)

[Put an [X] in the box for any configuration with significant answer changes.]

[ ] clm5_1

[ ] clm5_0

[ ] ctsm5_0-nwp

[ ] clm4_5


Bugs fixed or introduced
------------------------
CTSM issues fixed (include CTSM Issue #):
Fixes #1316
Fixes #1596

Notes of particular relevance for users
---------------------------------------
Details already discussed in the description above.

Notes of particular relevance for developers:
---------------------------------------------
Changes to tests or testing:
New tests are in place for this new code.

Testing summary:
----------------
[PASS means all tests PASS; OK means tests PASS other than expected fails.]

regular tests (aux_clm: https://github.com/ESCOMP/CTSM/wiki/System-Testing-Guide#pre-merge-system-testing):

cheyenne ---- OK
izumi ------- OK

Answer changes
--------------
Changes answers relative to baseline:
No, unless user chooses to run in non-default Meier2022 mode.

Other details
-------------
Pull Requests that document the changes (include PR ids):
https://github.com/ESCOMP/ctsm/pull/2045

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