! File %M% from Library %Q%
! Version %I% from %G% extracted: %H%
!------------------------------------------------------------------------------

REAL (KIND = ireals) FUNCTION SfcFlx_satwvpres (T, h_ice)

!------------------------------------------------------------------------------
!
! Description:
!
!  Computes saturation water vapour pressure 
!  over the water surface or over the ice surface
!  as function of temperature. 
!  
!
! Current Code Owner: DWD, Dmitrii Mironov
!  Phone:  +49-69-8062 2705
!  Fax:    +49-69-8062 3721
!  E-mail: dmitrii.mironov@dwd.de
!
! History:
! Version    Date       Name
! ---------- ---------- ----
! 1.00       2005/11/17 Dmitrii Mironov 
!  Initial release
! !VERSION!  !DATE!     <Your name>
!  <Modification comments>
!
! Code Description:
! Language: Fortran 90.
! Software Standards: "European Standards for Writing and
! Documenting Exchangeable Fortran 90 Code".
!==============================================================================
!
! Declarations:
!
! Modules used:

!_dm Parameters are USEd in module "SfcFlx".
!_nu USE data_parameters  , ONLY : &
!_nu     ireals,                   & ! KIND-type parameter for real variables
!_nu     iintegers                   ! KIND-type parameter for "normal" integer variables

!_dm The variable is USEd in module "SfcFlx".
!_nu USE flake_parameters , ONLY : &
!_nu   h_Ice_min_flk                 ! Minimum ice thickness [m]

!==============================================================================

IMPLICIT NONE

!==============================================================================
!
! Declarations
 
!  Input (function argument) 
REAL (KIND = ireals), INTENT(IN) ::   &
  T                                 , & ! Temperature [K]
  h_ice                                 ! Ice thickness [m]

!  Local parameters
REAL (KIND = ireals), PARAMETER ::   &
   b1_vap   = 610.78_ireals        , & ! Coefficient [N m^{-2} = kg m^{-1} s^{-2}]
   b3_vap   = 273.16_ireals        , & ! Triple point [K]
   b2w_vap  = 17.2693882_ireals    , & ! Coefficient (water)
   b2i_vap  = 21.8745584_ireals    , & ! Coefficient (ice) 
   b4w_vap  = 35.86_ireals         , & ! Coefficient (temperature) [K]
   b4i_vap  = 7.66_ireals              ! Coefficient (temperature) [K]

!==============================================================================
!  Start calculations
!------------------------------------------------------------------------------

! Saturation water vapour pressure [N m^{-2} = kg m^{-1} s^{-2}]

IF(h_ice.LT.h_Ice_min_flk) THEN  ! Water surface
  SfcFlx_satwvpres = b1_vap*EXP(b2w_vap*(T-b3_vap)/(T-b4w_vap))
ELSE                             ! Ice surface
  SfcFlx_satwvpres = b1_vap*EXP(b2i_vap*(T-b3_vap)/(T-b4i_vap))
END IF 

!------------------------------------------------------------------------------
!  End calculations
!==============================================================================

END FUNCTION SfcFlx_satwvpres