anchor.diff:            ! ----------------------------------------------
             CALL ussa_press(REAL(terrain_height(ixtrack,itimes),KIND=r8) / 1000.0_r8, &
                  local_psurf(ixtrack,itimes) )
  +          clima_psurf = REAL(Psurface(idx_lon, idx_lat), KIND=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
             ! Ap(1:CmEp1) & Bp(1:CmEp1) are coeff at layer boundary for pressure
  
positive.code:   ! ----------------------------
    ! 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
  
  
negative.code:   ! nt AMF calculations and contains necessary subroutines to read files
    ! and calculate them
    ! ====================================================================
    USE OMSAO_lininterpolation_module
    USE OMSAO_precision_module, ONLY: i4, r8, C_LONG, r4
    USE OMSAO_parameters_module
    USE OMSAO_errstat_module
  