subroutine calc_cpp_mugaz

!==================================================================
!     Purpose
!     -------
!     Compute the atmospheric specific heat capacity.
!     Compute the atmospheric mean molar mass.
!
!     Authors
!     ------- 
!     Robin Wordsworth (2009)
!
!==================================================================

      use gases_h
      implicit none

#include "comcstfi.h"
!#include "callkeys.h"

      integer igas

      cpp=0.0
      mugaz=0.0

      do igas=1,ngasmx

         if(igas.eq.vgas)then
            ! ignore variable gas in cpp calculation
         else
            ! all values at 300 K from Engineering Toolbox
            if(gnom(igas).eq.'CO2')then
               cpp   = cpp   + 0.846*gfrac(igas)
               mugaz = mugaz + 44.01*gfrac(igas)
            elseif(gnom(igas).eq.'N2_')then
               cpp   = cpp   + 1.040*gfrac(igas)
               mugaz = mugaz + 28.01*gfrac(igas)
            elseif(gnom(igas).eq.'H2_')then
               cpp   = cpp   + 14.31*gfrac(igas)
               mugaz = mugaz + 2.01*gfrac(igas)
            elseif(gnom(igas).eq.'H2O')then
               cpp   = cpp   + 1.864*gfrac(igas)
               mugaz = mugaz + 18.02*gfrac(igas)
            elseif(gnom(igas).eq.'CH4')then
               cpp   = cpp   + 2.226*gfrac(igas)
               mugaz = mugaz + 16.04*gfrac(igas)
            elseif(gnom(igas).eq.'NH3')then
               cpp   = cpp   + 2.175*gfrac(igas)
               mugaz = mugaz + 17.03*gfrac(igas)
               print*,'WARNING, cpp for NH3 may be for liquid' 
            else
               print*,'Error in calc_cpp_mugaz: Gas species not recognised!'
               call abort
            endif
         endif

      enddo

      cpp=1000.0*cpp

      print*,'Cp in calc_cpp_mugaz is ',cpp,'J kg^-1 K^-1'
      print*,'Mg in calc_cpp_mugaz is ',mugaz,'amu'

      R = 8.314511E+0 *1000.E+0/mugaz
      rcp = R/cpp

      return
    end subroutine calc_cpp_mugaz