bug-fix: use get_dist to calculate distances for observations with VE…

…RTISUNDEF

fixes #486

Previously observations with VERTISUNDEF were given a large distance, because
the verical coordinate is missing: local_array(3) == missing_r8

The location_mod::get_dist uses horizontal distance only if
VERTISUNDEF for either location.

models/wrf/model_mod.f90

@@ -6403,6 +6403,13 @@ subroutine get_close(gc, base_loc, base_type, locs, loc_qtys, &
       local_loc   = locs(t_ind)
       local_which = nint(query_location(local_loc))
 
+      if (present(dist)) then
+         if (local_which == VERTISUNDEF) then
+            dist(k) = get_dist(base_loc, local_loc, base_type, loc_qtys(t_ind))
+            cycle
+         endif
+      endif
+
       ! Convert local vertical coordinate to requested vertical coordinate if necessary.
       ! This should only be necessary for obs priors, as state location information already
       ! contains the correct vertical coordinate (filter_assim's call to get_state_meta_data).