anchor.diff:  
       end subroutine compute_p_offset
   
  -    !>----------------------------------------------------------
  -    !! Compute the height of level z_out based on the pressure at z, z_out,
  -    !! and the temperature and humidity in between them
  -    !!
  -    !! Input temperature is real temperature in Kelvin  [K]
  -    !! Input humidity is mixing ratio                   [kg/kg]
  -    !! Input pressures are in Pascals                   [Pa]
  -    !! Heights (input and output) are in meters         [m]
  -    !!
  -    !!----------------------------------------------------------
  -    subroutine compute_z_offset(z_out, z, p0, p1, t, qv)
  -        implicit none
  -        real, intent(inout),    dimension(:,:)   :: z_out   !
  -        real, intent(in),       dimension(:,:)   :: z       !
  -        real, intent(in),       dimension(:,:)   :: p0      !
  -        real, intent(in),       dimension(:,:)   :: p1      !
  -        real, intent(in),       dimension(:,:)   :: t       !
  -        real, intent(in),       dimension(:,:)   :: qv      !
  -
  -        z_out = z - &
  -                Rd / gravity * ( t * ( 1 + 0.608 * qv ) ) * &
  -                LOG ( p1 / p0 )
  -
  -        ! note: WRF formulate to compute height from pressure
  -        ! z(k) = z(k-1) - &
  -        !     R_d / g * 0.5 * ( t(k) * ( 1 + 0.608 * qv(k) ) +   &
  -        !                     t(k-1) * ( 1 + 0.608 * qv(k-1) ) ) * &
  -        !     LOG ( p(k) / p(k-1) )
  -
  -    end subroutine compute_z_offset
  +    ! !>----------------------------------------------------------
  +    ! !! Compute the height of level z_out based on the pressure at z, z_out,
  +    ! !! and the temperature and humidity in between them
  +    ! !!
  +    ! !! Input temperature is real temperature in Kelvin  [K]
  +    ! !! Input humidity is mixing ratio                   [kg/kg]
  +    ! !! Input pressures are in Pascals                   [Pa]
  +    ! !! Heights (input and output) are in meters         [m]
  +    ! !!
  +    ! !!----------------------------------------------------------
  +    ! subroutine compute_z_offset(z_out, z, p0, p1, t, qv)
  +    !     implicit none
  +    !     real, intent(inout),    dimension(:,:)   :: z_out   !
  +    !     real, intent(in),       dimension(:,:)   :: z       !
  +    !     real, intent(in),       dimension(:,:)   :: p0      !
  +    !     real, intent(in),       dimension(:,:)   :: p1      !
  +    !     real, intent(in),       dimension(:,:)   :: t       !
  +    !     real, intent(in),       dimension(:,:)   :: qv      !
  +    !
  +    !     z_out = z - &
  +    !             Rd / gravity * ( t * ( 1 + 0.608 * qv ) ) * &
  +    !             LOG ( p1 / p0 )
  +    !
  +    !     ! note: WRF formulate to compute height from pressure
  +    !     ! z(k) = z(k-1) - &
  +    !     !     R_d / g * 0.5 * ( t(k) * ( 1 + 0.608 * qv(k) ) +   &
  +    !     !                     t(k-1) * ( 1 + 0.608 * qv(k-1) ) ) * &
  +    !     !     LOG ( p(k) / p(k-1) )
  +    !
  +    ! end subroutine compute_z_offset
   
       !>----------------------------------------------------------
       !! Convert relative humidity, temperature, and pressure to water vapor mixing ratio
  
positive.code:     !! Change in height is in meters                    [m]
      !!
      !!----------------------------------------------------------
      subroutine compute_3d_p(p, ps, z, t, qv, zs)
          implicit none
          real, intent(inout)        , dimension(:,:,:)   :: p
          real, intent(in)           , dimension(:,:)     :: ps
          real, intent(in)           , dimension(:,:,:)   :: z
          real, intent(in)           , dimension(:,:,:)   :: t
          real, intent(in)           , dimension(:,:,:)   :: qv
          real, intent(in),  optional, dimension(:,:)     :: zs
  
          integer :: i
  
  
negative.code: 
  
      !>----------------------------------------------------------
      !! Compute a 3D height field given a surface (or sea level) pressure
      !! and 3D temperature, humidity and pressures.
      !!
      !! Input temperature is real temperature in Kelvin  [K]
      !! Input humidity is mixing ratio                   [kg/kg]
  