new b-case w/ wsub_scale and wscale_floor reduced

[adamrher]

Description:

same as #362 except the hard coded floor value of wsub is also scaled by 0.5 (10->5 cm/s). The SourceMods for the new floor value: /glade/u/home/aherring/src/cam6_3_115/usr_src/wsubfloor/ndrop.F90

Case directory:
Locally (if still available):
/glade/p/cesmdata/cseg/runs/cesm2_0/$CASE

On github:
https://github.com/NCAR/amwg_dev/tree/$CASE

Sandbox:
Locally (if still available):
/glade/work/hannay/cesm_tags/cesm2_3_alpha13b

On github:

git clone https://github.com/ESCOMP/cesm cesm2_3_alpha13b
cd cesm2_3_alpha13b
git checkout  cesm2_3_alpha13b
./manage_externals/checkout_externals -o

Diagnostics:
AMWG diags (if available)
https://webext.cgd.ucar.edu/BLT1850/$CASE/atm/

Contacts:

@JulioTBacmeister @PeterHjortLauritzen @adamrher

[cecilehannay]

See run #366