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subroutine da_add_noise (fld, yo, z) 77,3
!-----------------------------------------------------------------------
! Purpose: TBD
!-----------------------------------------------------------------------
implicit none
type (field_type), intent(inout) :: fld ! O-B sub-type.
real, intent(inout) :: yo ! Observation.
real, intent(out) :: z ! Random number.
real :: noise
if (trace_use) call da_trace_entry
("da_add_noise")
z = missing_r
if (fld % qc >= obs_qc_pointer) then
! [1] Calculate scaled Gaussian noise:
call da_gauss_noise (z)
noise = fld % error * z
! [3] Recalculate corresponding O and O-B:
yo = yo + noise
fld % inv = fld % inv + noise
end if
if (trace_use) call da_trace_exit("da_add_noise")
end subroutine da_add_noise