Line data    Source code

       1             : ! This code is part of RRTM for GCM Applications - Parallel (RRTMGP)
       2             : !
       3             : ! Contacts: Robert Pincus and Eli Mlawer
       4             : ! email:  rrtmgp@aer.com
       5             : !
       6             : ! Copyright 2015-,  Atmospheric and Environmental Research,
       7             : ! Regents of the University of Colorado, Trustees of Columbia University.  All right reserved.
       8             : !
       9             : ! Use and duplication is permitted under the terms of the
      10             : !    BSD 3-clause license, see http://opensource.org/licenses/BSD-3-Clause
      11             : ! -------------------------------------------------------------------------------------------------
      12             : !> ##  Physical and mathematical constants used in RRTMGP gas optics calculation
      13             : !>
      14             : !>   If the host model in which RRTGMP is embedded has defined these constants elsewhere
      15             : !>   the model definitions can be used instead by renaming. For example,
      16             : !> ```use  mo_model_constants, only k_boltz => boltzman_k, ...```
      17             : !>   where the syntax is local_name => original_name
      18             : !>   and all the local names need to be defined
      19             : !
      20             : !> "Constants" specific to the earth's atmosphere should also be made consistent with the
      21             : !>   host model but may be changed in a call to init_constants(), normally at initialization
      22             : ! -------------------------------------------------------------------------------------------------
      23             : module mo_gas_optics_constants
      24             :   use mo_rte_kind, only: wp
      25             :   public
      26             : 
      27             :   ! -----------------------------------------
      28             :   ! Physical constants, 2018 SI defintion of metric system
      29             :   !   doi:10.1088/1681-7575/aa950a (see also https://www.nist.gov/si-redefinition/meet-constants)
      30             :   ! Boltzmann constant [J/K] = [(kg m^2)/(K s^2)]
      31             :   real(wp), parameter :: k_boltz = 1.380649e-23_wp
      32             : 
      33             :   !  molecular weight of water [kg/mol]
      34             :   real(wp), parameter :: m_h2o =  0.018016_wp
      35             : 
      36             :   ! Avogadro's number [molec/mol]
      37             :   real(wp), parameter :: avogad = 6.02214076e23_wp
      38             : 
      39             :   ! Universal gas constant [J/(mol K)]
      40             :   real(wp), parameter :: R_univ_gconst = avogad * k_boltz
      41             : 
      42             :   ! -----------------------------------------
      43             :   !
      44             :   ! Constants specific to the earth's atmosphere -- changeable in init() because they
      45             :   !   might be different on e.g. other planets
      46             : 
      47             :   ! molecular weight of dry air [kg/mol]
      48             :   real(wp), protected :: m_dry = 0.028964_wp
      49             : 
      50             :   ! Gravity at Earth's surface [m/s2]
      51             :   real(wp), protected :: grav = 9.80665_wp
      52             : 
      53             :   ! Specific heat at constant pressure for dry air [J/(K kg)]
      54             :   real(wp), protected :: cp_dry = 1004.64_wp
      55             : 
      56             : contains
      57             :   ! -----------------------------------------
      58           0 :   subroutine init_constants(gravity, mol_weight_dry_air, heat_capacity_dry_air)
      59             :     real(wp), optional, intent(in) :: gravity, mol_weight_dry_air, heat_capacity_dry_air
      60             :       !! Planetary and atmospheric values used by RRTMGP in computing gas optical properties
      61             :       !! Default values reflect modern Earth but these can be changed using this routine
      62             : 
      63           0 :     if(present(gravity))               grav   = gravity
      64           0 :     if(present(mol_weight_dry_air))    m_dry  = mol_weight_dry_air
      65           0 :     if(present(heat_capacity_dry_air)) cp_dry = heat_capacity_dry_air
      66             : 
      67           0 :   end subroutine init_constants
      68             :   ! -----------------------------------------
      69             : end module mo_gas_optics_constants