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subroutine da_random_omb(std_dev, yo, qc_flag, omb) 76,3
!-----------------------------------------------------------------------
! Purpose: TBD
!-----------------------------------------------------------------------
implicit none
real, intent(in) :: std_dev ! Standard deviation scaling.
real, intent(inout) :: yo ! Observatopn.
integer, intent(in) :: qc_flag ! Ob QC flag.
real, intent(inout) :: omb ! O-B.
real :: xb ! Background value.
real :: z ! Gaussian noise.
if (trace_use) call da_trace_entry
("da_random_omb")
if (qc_flag >= obs_qc_pointer) then
! [1] Calculate background value from old O, O-B:
xb = yo - omb
! [2] Calculate new O-B as scaled Gaussian noise:
call da_gauss_noise(z)
omb = set_omb_rand_fac * std_dev * z
! [3] Recalculate corresponding observation:
yo = xb + omb
end if
if (trace_use) call da_trace_exit("da_random_omb")
end subroutine da_random_omb