bug: wrf model_mod QTY_VAPOR_MIXING_RATIO with vertissurface always returns 0.0 with success if q2 is not in the state

[hkershaw-brown]

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Describe the bug

1. List the steps someone needs to take to reproduce the bug.
   Run model_mod_check with

   &model_mod_check_nml
       ...
       loc_of_interest       = 1.715, 45.732, 1
       quantity_of_interest  = 'QTY_VAPOR_MIXING_RATIO'
       interp_test_vertcoord = 'VERTISSURFACE'
       ...
   /   
   

2. What was the expected outcome?
   Interpolate using type_q2 if present or fail.
3. What actually happened?

Error Message

Here is some prints to show the value of fld (q2)

interpolating at  Lon/Lat(deg):   1.71500000  45.73200000  Vert:      1.00000 surface (m)
interpolating for "QTY_VAPOR_MIXING_RATIO"
-------------------------------------------------------------

 hello helen surface elevation obs kind           20
 hello helen q2  -888888.00000000000       -888888.00000000000     
member     1, SUCCESS with value    ::    0.0000000000000000

Surface variable:

DART/models/wrf/model_mod.f90

Line 1242 in a32ab03

elseif(is_vertical(location,"SURFACE") .or. obs_kind == QTY_SURFACE_ELEVATION) then

Checks for q2, if not there fld gets set to 0 because -88888 is < 0 (! Don't accept negative water vapor amounts), model_interpolate returns 'success'

DART/models/wrf/model_mod.f90

Lines 2050 to 2063 in a32ab03

	if(.not. surf_var) then
	call simple_interp_distrib(fld, wrf, id, i, j, k, obs_kind, dxm, dx, dy, dym, uniquek, ens_size, state_handle )
	if (all(fld == missing_r8)) goto 200
	else ! This is for surface QV (Q2)
	! Confirm that right field is in the DART state vector
	if ( wrf%dom(id)%type_q2 >= 0 ) then
	!HK I am not sure what the type should be
	call surface_interp_distrib(fld, wrf, id, i, j, obs_kind, wrf%dom(id)%type_q2, dxm, dx, dy, dym, ens_size, state_handle)
	if (all(fld == missing_r8)) goto 200
	endif
	endif
	! Don't accept negative water vapor amounts
	fld = max(0.0_r8, fld)

Which model(s) are you working with?

wrf

Version of DART

Which version of DART are you using?
v11.19.0-39-g41563ddd5

Have you modified the DART code?

Yes, but I believe also present on main
Edit: confirmed on main

Build information

Please describe:

1. Mac M
2. GNU Fortran (MacPorts gcc13 13.3.0_2+stdlib_flag) 13.3.0