Add Turbulent Orographic Form Drag to SFCLAY

[Songyou184]

TYPE: new feature

KEYWORDS: surface layer, turbulent form drag

SOURCE: Songyou Hong

DESCRIPTION OF CHANGES:
Turbulent form drag (TOFD) was added in computing surface drag (kim_tofd=.true., default). A factor for TOFD was added (tofd_factor=.003, default).

LIST OF MODIFIED FILES:
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:
The Jenkins tests are all passing.

RELEASE NOTE: This PR adds a scale-aware turbulent orographic form drag option (kim_tofd) in revised MM5 surface layer scheme. The default value for the option is on and it would increase surface drag. Use this new option with care.

[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

[dudhia]

Needs updating to resolve conflicts.

[dudhia]

Updated code

[weiwangncar]

@Songyou184 @dudhia Can you update the PR message? Thanks!

[weiwangncar]

@Songyou184 @dudhia If you can add some notes on expected outcome, that would be nice.