constants.F90

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!! \brief Defines useful constants for Earth. Constants are defined as real
!! parameters. Constants are accessed through the "use" statement.
!!
!! \author Bruce Wyman <Bruce.Wyman@noaa.gov>
module constants_mod

!---variable for strong typing grid parameters
use platform_mod, only: r8_kind
implicit none
private

! Include variable "version" to be written to log file.
#include<file_version.h>
!-----------------------------------------------------------------------
! version is public so that write_version_number can be called for constants_mod
! by fms_init
public :: version

real :: realnumber !< dummy variable to use in HUGE initializations

#ifdef GFS_PHYS
! SJL: the following are from fv3_gfsphysics/gfs_physics/physics/physcons.f90
real,               public, parameter :: radius = 6.3712e+6_r8_kind           !< Radius of the Earth [m]
real(kind=r8_kind), public, parameter :: pi_8   = 3.1415926535897931_r8_kind  !< Ratio of circle circumference to diameter [N/A]
real,               public, parameter :: pi     = 3.1415926535897931_r8_kind  !< Ratio of circle circumference to diameter [N/A] (REAL(KIND=8))
real,               public, parameter :: omega  = 7.2921e-5_r8_kind   !< Rotation rate of the Earth [1/s]
real,               public, parameter :: grav   = 9.80665_r8_kind     !< Acceleration due to gravity [m/s^2]
real(kind=r8_kind), public, parameter :: grav_8 = 9.80665_r8_kind     !< Acceleration due to gravity [m/s^2] (REAL(KIND=8))
real,               public, parameter :: rdgas  = 287.05_r8_kind      !< Gas constant for dry air [J/kg/deg]
real,               public, parameter :: rvgas  = 461.50_r8_kind      !< Gas constant for water vapor [J/kg/deg]
! Extra:
real,               public, parameter :: hlv      = 2.5e6_r8_kind     !< Latent heat of evaporation [J/kg]
real,               public, parameter :: hlf      = 3.3358e5_r8_kind  !< Latent heat of fusion [J/kg]
real,               public, parameter :: con_cliq = 4.1855e+3_r8_kind !< spec heat H2O liq [J/kg/K]
real,               public, parameter :: con_csol = 2.1060e+3_r8_kind !< spec heat H2O ice [J/kg/K]
real,               public, parameter :: cp_air = 1004.6_r8_kind      !< Specific heat capacity of dry air at constant pressure [J/kg/deg]
real,               public, parameter :: kappa  = rdgas/cp_air        !< RDGAS / CP_AIR [dimensionless]
real,               public, parameter :: tfreeze = 273.15_r8_kind     !< Freezing temperature of fresh water [K]
#else

#ifdef SMALL_EARTH
#if defined(DCMIP) || (defined(HIWPP) && defined(SUPER_K))
 real, private, parameter :: small_fac =  1._r8_kind / 120._r8_kind #only needed for supercell test
#elif defined(HIWPP)
 real, private, parameter :: small_fac = 1._r8_kind / 166.7_r8_kind
#else
 real, private, parameter :: small_fac = 1._r8_kind / 10._r8_kind
#endif
#else
 real, private, parameter :: small_fac = 1._r8_kind
#endif

real,         public, parameter :: radius = 6371.0e+3_r8_kind * small_fac   !< Radius of the Earth [m]
real(kind=8), public, parameter :: pi_8   = 3.14159265358979323846_r8_kind  !< Ratio of circle circumference to diameter [N/A]
real,         public, parameter :: pi     = 3.14159265358979323846_r8_kind  !< Ratio of circle circumference to diameter [N/A]
real,         public, parameter :: omega  = 7.292e-5_r8_kind / small_fac    !< Rotation rate of the Earth [1/s]
real,         public, parameter :: grav   = 9.80_r8_kind             !< Acceleration due to gravity [m/s^2]
real,         public, parameter :: rdgas  = 287.04_r8_kind           !< Gas constant for dry air [J/kg/deg]
real,         public, parameter :: rvgas  = 461.50_r8_kind           !< Gas constant for water vapor [J/kg/deg]
! Extra:
real,         public, parameter :: hlv = 2.500e6_r8_kind             !< Latent heat of evaporation [J/kg]
real,         public, parameter :: hlf = 3.34e5_r8_kind              !< Latent heat of fusion [J/kg]
real,         public, parameter :: kappa  = 2.0_r8_kind/7.0_r8_kind  !< RDGAS / CP_AIR [dimensionless]
real,         public, parameter :: cp_air = rdgas/kappa              !< Specific heat capacity of dry air at constant pressure [J/kg/deg]
real,         public, parameter :: tfreeze = 273.16_r8_kind          !< Freezing temperature of fresh water [K]
#endif

real, public, parameter :: stefan  = 5.6734e-8_r8_kind !< Stefan-Boltzmann constant [W/m^2/deg^4]

real, public, parameter :: cp_vapor = 4.0_r8_kind*rvgas      !< Specific heat capacity of water vapor at constant pressure [J/kg/deg]
real, public, parameter :: cp_ocean = 3989.24495292815_r8_kind !< Specific heat capacity taken from McDougall (2002) 
                                                               !! "Potential Enthalpy ..." [J/kg/deg]
real, public, parameter :: rho0    = 1.035e3_r8_kind  !< Average density of sea water [kg/m^3]
real, public, parameter :: rho0r   = 1.0_r8_kind/rho0 !< Reciprocal of average density of sea water [m^3/kg]
real, public, parameter :: rho_cp  = rho0*cp_ocean    !< (kg/m^3)*(cal/kg/deg C)(joules/cal) = (joules/m^3/deg C) [J/m^3/deg]

real, public, parameter :: es0 = 1.0_r8_kind        !< Humidity factor. Controls the humidity content of the atmosphere through
                                                    !! the Saturation Vapour Pressure expression when using DO_SIMPLE. [dimensionless]
real, public, parameter :: dens_h2o = 1000._r8_kind !< Density of liquid water [kg/m^3]
real, public, parameter :: hls = hlv + hlf          !< Latent heat of sublimation [J/kg]

real, public, parameter :: wtmair   = 2.896440e+01_r8_kind   !< Molecular weight of air [AMU]
real, public, parameter :: wtmh2o   = wtmair*(rdgas/rvgas)   !< Molecular weight of water [AMU]
real, public, parameter :: wtmozone =  47.99820_r8_kind      !< Molecular weight of ozone [AMU]
real, public, parameter :: wtmc     =  12.00000_r8_kind      !< Molecular weight of carbon [AMU]
real, public, parameter :: wtmco2   =  44.00995_r8_kind      !< Molecular weight of carbon dioxide [AMU]
real, public, parameter :: wtmch4   =  16.0425_r8_kind       !< Molecular weight of methane [AMU]
real, public, parameter :: wtmo2    =  31.9988_r8_kind       !< Molecular weight of molecular oxygen [AMU]
real, public, parameter :: wtmcfc11 = 137.3681_r8_kind       !< Molecular weight of CFC-11 (CCl3F) [AMU]
real, public, parameter :: wtmcfc12 = 120.9135_r8_kind       !< Molecular weight of CFC-21 (CCl2F2) [AMU]
real, public, parameter :: wtmn     =  14.0067_r8_kind       !< Molecular weight of Nitrogen [AMU]
real, public, parameter :: diffac   = 1.660000e+00_r8_kind   !< Diffusivity factor [dimensionless]
real, public, parameter :: avogno   = 6.023000e+23_r8_kind   !< Avogadro's number [atoms/mole]
real, public, parameter :: pstd     = 1.013250e+06_r8_kind   !< Mean sea level pressure [dynes/cm^2]
real, public, parameter :: pstd_mks = 101325.0_r8_kind       !< Mean sea level pressure [N/m^2]

real, public, parameter :: seconds_per_day    = 8.640000e+04_r8_kind !< Seconds in a day [s]
real, public, parameter :: seconds_per_hour   = 3600._r8_kind        !< Seconds in an hour [s]
real, public, parameter :: seconds_per_minute = 60._r8_kind          !< Seconds in a minute [s]
real, public, parameter :: rad_to_deg         = 180._r8_kind/pi      !< Degrees per radian [deg/rad]
real, public, parameter :: deg_to_rad         = pi/180._r8_kind      !< Radians per degree [rad/deg]
real, public, parameter :: radian             = rad_to_deg           !< Equal to RAD_TO_DEG for backward compatability. [rad/deg]
real, public, parameter :: alogmin            = -50.0_r8_kind        !< Minimum value allowed as argument to log function [N/A]
real, public, parameter :: epsln              = 1.0e-40_r8_kind      !< A small number to prevent divide by zero exceptions [N/A]

real, public, parameter :: radcon = ((1.0e+02*grav)/(1.0e+04*cp_air))*seconds_per_day !< Factor used to convert flux divergence to
                                                                                      !! heating rate in degrees per day [deg sec/(cm day)]
real, public, parameter :: radcon_mks  = (grav/cp_air)*seconds_per_day !< Factor used to convert flux divergence to
                                                                       !! heating rate in degrees per day [deg sec/(m day)]
real, public, parameter :: o2mixrat    = 2.0953e-01_r8_kind !< Mixing ratio of molecular oxygen in air [dimensionless]
real, public, parameter :: rhoair      = 1.292269_r8_kind   !< Reference atmospheric density [kg/m^3]
real, public, parameter :: vonkarm     = 0.40_r8_kind       !< Von Karman constant [dimensionless]
real, public, parameter :: c2dbars     = 1.e-4_r8_kind      !< Converts rho*g*z (in mks) to dbars: 1dbar = 10^4 (kg/m^3)(m/s^2)m [dbars]
real, public, parameter :: kelvin      = 273.15_r8_kind     !< Degrees Kelvin at zero Celsius [K]

public :: constants_init

contains

!> \brief dummy routine.
subroutine constants_init

end subroutine constants_init

end module constants_mod

!   <FUTURE>
!   1.  Renaming of constants.
!   </FUTURE>
!   <FUTURE>
!   2.  Additional constants.
!   </FUTURE>
!   <NOTE>
!    Constants have been declared as type REAL, PARAMETER.
!
!    The value a constant can not be changed in a users program.
!    New constants can be defined in terms of values from the
!    constants module using a parameter statement.<br><br>
!
!    The name given to a particular constant may be changed.<br><br>
!
!    Constants can be used on the right side on an assignment statement
!    (their value can not be reassigned).
!
!
!<TESTPROGRAM NAME="EXAMPLE">
!<PRE>
!    use constants_mod, only:  TFREEZE, grav_new => GRAV
!    real, parameter :: grav_inv = 1.0 / grav_new
!    tempc(:,:,:) = tempk(:,:,:) - TFREEZE
!    geopotential(:,:) = height(:,:) * grav_new
!</PRE>
!</TESTPROGRAM>
!   </NOTE>