!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!                                                                       !!
!!                   GNU General Public License                          !!
!!                                                                       !!
!! This file is part of the Flexible Modeling System (FMS).              !!
!!                                                                       !!
!! FMS is free software; you can redistribute it and/or modify           !!
!! it and are expected to follow the terms of the GNU General Public     !!
!! License as published by the Free Software Foundation.                 !!
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!! FMS is distributed in the hope that it will be useful,                !!
!! but WITHOUT ANY WARRANTY; without even the implied warranty of        !!
!! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         !!
!! GNU General Public License for more details.                          !!
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!! You should have received a copy of the GNU General Public License     !!
!! along with FMS; if not, write to:                                     !!
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!! or see:                                                               !!
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!!                                                                       !!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

MODULE constants_mod

!-----------------------------------------------------
!
!  Defines useful constants for Earth in mks units.
!
!-----------------------------------------------------

!use fms_mod, only: write_version_number

IMPLICIT NONE
PRIVATE

CHARACTER(len=128) :: version='$Id: constants.f90,v 1.1 2002/03/27 22:43:06 alangenh Exp $'
CHARACTER(len=128) :: tagname='$Name: galway $'
LOGICAL :: do_log = .TRUE.
LOGICAL :: module_is_initialized = .FALSE.
!-----------------------------------------------------------------------
!------------ physical constants ---------------

REAL, PUBLIC, PARAMETER :: RADIUS = 6376.e3      !  radius of the earth (meters)
REAL, PUBLIC, PARAMETER :: OMEGA  = 7.292e-5     !  rotation rate of planet (1/sec)
REAL, PUBLIC, PARAMETER :: GRAV   = 9.80         !  acceleration due to gravity (m/s2)
REAL, PUBLIC, PARAMETER :: RDGAS  = 287.04       !  gas constant for dry air (J/Kg/deg)
REAL, PUBLIC, PARAMETER :: KAPPA  = 2./7.        !  RDGAS / CP
REAL, PUBLIC, PARAMETER :: cp     = RDGAS/KAPPA  !  spec heat cap of dry air (J/kg/deg)

!------------ water vapor constants ---------------

REAL, PUBLIC, PARAMETER :: RVGAS = 461.50        !  gas constant for water vapor (J/Kg/deg)
REAL, PUBLIC, PARAMETER :: DENS_H2O = 1000.      !  density of liquid water (Kg/m3)
REAL, PUBLIC, PARAMETER :: HLV = 2.500e6         !  latent heat of evaporation (J/Kg)
REAL, PUBLIC, PARAMETER :: HLF = 3.34e5          !  latent heat of fusion (J/Kg)
REAL, PUBLIC, PARAMETER :: HLS = 2.834e6         !  latent heat of sublimation (J/Kg)
REAL, PUBLIC, PARAMETER :: TFREEZE = 273.16      !  temp where fresh water freezes (deg K)

!------------ miscellaneous constants ---------------

REAL, PUBLIC, PARAMETER :: STEFAN  =  5.6734e-8  !  Stefan-Boltzmann constant (W/m2/deg4)
REAL, PUBLIC, PARAMETER :: VONKARM =  0.40       !  Von Karman constant
REAL, PUBLIC, PARAMETER :: PI      =  3.14159265358979323846 ! is it enough?
!-----------------------------------------------------------------------

PUBLIC constants_init

CONTAINS

! optional initialization routine
! only purpose is to write version to log file

SUBROUTINE constants_init

  IF (module_is_initialized) RETURN
  module_is_initialized = .TRUE.

  IF (.NOT.do_log) RETURN
!  call write_version_number (version,tagname)
  do_log = .FALSE.

END SUBROUTINE constants_init

!-----------------------------------------------------------------------

END MODULE constants_mod