anchor.diff:  
   END SUBROUTINE read_lookup_table
   
  +SUBROUTINE ussa_press (altitude,pressure)
  +
  +  ! -----------------------------
  +  ! Adapted from GAMAP ussa_press
  +  ! -----------------------------
  +  IMPLICIT NONE
  +
  +  ! ----------------------------
  +  ! Input variable (altitude km)
  +  ! ----------------------------
  +  REAL(KIND=r8), INTENT(IN) :: altitude
  +  
  +  ! ------------------------------
  +  ! Output variable (pressure hPa)
  +  ! ------------------------------
  +  REAL(KIND=r8), INTENT(OUT) :: pressure
  +
  +  ! ---------------------------------------------
  +  ! Polynomial coefficients to work outp pressure
  +  ! ---------------------------------------------
  +  REAL(KIND=r8), DIMENSION(6), PARAMETER :: coeff = (/ &
  +       2.99955D+00, -4.61994D-02, &
  +       -1.55620D-03, 4.57018D-05, &
  +       -5.14580D-07, 1.94170D-09 /)
  +
  +  ! -----------------
  +  ! Work out pressure
  +  ! -----------------
  +  pressure = &
  +       coeff(1) + &
  +       coeff(2) * altitude**1 + &
  +       coeff(3) * altitude**2 + &
  +       coeff(4) * altitude**3 + &
  +       coeff(5) * altitude**4 + &
  +       coeff(6) * altitude**5
  +
  +  pressure = 10**pressure
  +  
  +END SUBROUTINE ussa_press
  +
   END MODULE OMSAO_wfamf_module
   
  
positive.code: 
            ! ----------------------------------------------
            ! Convert pixel terrain height to pressure using
            ! Xiong suggested to use pressure altitude:
            !  Z = -16 alog10 (P / Po) Z in km and P in hPa.
            ! From OMI L1B file.
            ! ----------------------------------------------
            local_psurf(ixtrack,itimes) = 1013.0_r8 * &
                 (10.0_r8 ** (REAL(terrain_height(ixtrack,itimes),KIND=r8) / 1000.0_r8 / (-16.0_r8)))
  
            clima_psurf = REAL(Psurface(idx_lon, idx_lat), KIND=r8)
            ! lpre(0:CmETA) is pressure at layer boundaries, same unit as
            ! local_surf, convert from hPa to Pa, it is a CmETA+1 = CmEp1 array
  
negative.code:           ! Xiong suggested to use pressure altitude:
            !  Z = -16 alog10 (P / Po) Z in km and P in hPa.
            ! ----------------------------------------------
            CALL ussa_press(local_srf(1) / 1000.0_r8, local_srf(1))
  
            !Bringing surface pressure to highest available in lookup table if needed
            !Current highest surface pressure is 1030 hPa.
  