SFCLAY 2026 : # 1 of GWDO-SHPBL PR

[Songyou184]

TYPE: new feature

KEYWORDS: surface layer, drag

SOURCE: Songyou Hong

DESCRIPTION OF CHANGES:
Problem:
Generally or specifically, what was wrong and needed to be addressed?

Solution:
What was down algorithmically and in the source code to address the problem?

LIST OF MODIFIED FILES: list of changed files (use git diff --name-status master to get formatted list)
M arch/Externals.cfg
M dyn_em/module_first_rk_step_part1.F
M phys/module_sf_sfclayrev.F
M phys/module_surface_driver.F

TESTS CONDUCTED:

1. Do mods fix problem? How can that be demonstrated, and was that test conducted?
2. The Jenkins tests are all passing.

RELEASE NOTE: Include a stand-alone message suitable for the inclusion in the minor and annual releases. A publication citation is appropriate.

[dudhia]

Note for @islas and @weiwangncar
Songyou is splitting his PR into three parts. This currently uses manage_externals which probably needs changing.

[weiwangncar]

@Songyou184 @dudhia See my email on how to use submodules.

[weiwangncar]

The regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None