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17 Physical Constants

The CCSM code has a mechanism for facilitating the consistent use of constants among the various CCSM components - this is the "shared constants" module of the CCSM shared code library. The Coupler always uses shared constants whenever possible and only defines a constant locally if no such constant is available from the shared constants module.

The Coupler source code itself (found in .../models/cpl/cpl6/ ) is incomplete and cannot be compiled (due to missing subroutines) unless it is compiled along with CCSM shared code (found in .../models/csm_share/ ). This shared code includes the shared constants module.

Constants in the Coupler whose actual values come from the shared constants...

  cpl_const_pi          = SHR_CONST_PI          ! pi
  cpl_const_rearth      = SHR_CONST_REARTH      ! radius of earth ~ m
  cpl_const_g           = SHR_CONST_G           ! acceleration of gravity
  cpl_const_cpdair      = SHR_CONST_CPDAIR      ! specific heat of dry air
  cpl_const_cpwv        = SHR_CONST_CPWV        ! specific heat of water vapor
  cpl_const_cpvir       = cpl_const_cpwv/cpl_const_cpdair - 1.0
  cpl_const_zvir        = SHR_CONST_ZVIR        ! rh2o/rair   - 1.0
  cpl_const_latvap      = SHR_CONST_LATVAP      ! latent heat of evaporation
  cpl_const_latice      = SHR_CONST_LATICE      ! latent heat of fusion
  cpl_const_stebol      = SHR_CONST_STEBOL      ! Stefan-Boltzmann
  cpl_const_karman      = SHR_CONST_KARMAN      ! Von Karman constant
  cpl_const_ocn_ref_sal = SHR_CONST_OCN_REF_SAL ! ocn reference salinity
  cpl_const_ice_ref_sal = SHR_CONST_ICE_REF_SAL ! ice reference salinity
  cpl_const_spval       = SHR_CONST_SPVAL       ! special value
  HFLXtoWFLX   = -(So-Si)/(So*latice)  ! converts heat to water for diagnostics

The actual values for the shared constants above...

  SHR_CONST_PI     = 3.14159265358979323846  ! pi
  SHR_CONST_REARTH = 6.37122e6    ! radius of earth ~ m
  SHR_CONST_G      = 9.80616      ! acceleration of gravity ~ m/s^2
  SHR_CONST_CPDAIR = 1.00464e3    ! specific heat of dry air ~ J/kg/K
  SHR_CONST_CPWV   = 1.810e3      ! specific heat of water vap ~ J/kg/K
  SHR_CONST_ZVIR   = (SHR_CONST_RWV/SHR_CONST_RDAIR)-1.0   ! RWV/RDAIR - 1.0
  SHR_CONST_LATVAP = 2.501e6      ! latent heat of evaporation ~ J/kg
  SHR_CONST_LATICE = 3.337e5      ! latent heat of fusion ~ J/kg
  SHR_CONST_STEBOL = 5.67e-8      ! Stefan-Boltzmann constant ~ W/m^2/K^4
  SHR_CONST_KARMAN = 0.4          ! Von Karman constant
  SHR_CONST_OCN_REF_SAL = 34.7    ! ocn ref salinity (psu)
  SHR_CONST_ICE_REF_SAL =  4.0    ! ice ref salinity (psu)

  SHR_CONST_RWV   = 
     SHR_CONST_RGAS/SHR_CONST_MWWV    ! Water vapor gas constant ~ J/K/kg
  SHR_CONST_RDAIR = 
     SHR_CONST_RGAS/SHR_CONST_MWDAIR  ! Dry air gas constant     ~ J/K/kg
  SHR_CONST_RGAS  = 
     SHR_CONST_AVOGAD*SHR_CONST_BOLTZ ! Universal gas constant   ~ J/K/mole
  SHR_CONST_MWWV   = 18.016           ! molecular weight water vapor
  SHR_CONST_MWDAIR = 28.966           ! molecular weight dry air ~ kg/kmole
  SHR_CONST_BOLTZ  = 1.38065e-23      ! Boltzmann's constant ~ J/K/molecule
  SHR_CONST_AVOGAD = 6.02214e26       ! Avogadro's number ~ molecules/kmole

Constants in the Coupler whose values do not come from the shared constants...

  albdif = 0.06   ! 60 deg reference albedo, diffuse for ocn albedo calc
  albdir = 0.07   ! 60 deg reference albedo, direct  for ocn albedo calc
  umin   =  0.5   ! minimum wind speed (m/s)       for atm/ocn flux calc
  zref   = 10.0   ! reference height (m)           for atm/ocn flux calc
  ztref  =  2.0   ! reference height for air T (m) for atm/ocn flux calc
  spval  = 1.0e30 ! flags special value (missing value)



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