Line data    Source code

       1             : !----------------------------------------------------------------------------------
       2             : ! low level utility module for cloud aerosols
       3             : !
       4             : ! Created by Francis Vitt
       5             : !----------------------------------------------------------------------------------
       6             : module cldaero_mod
       7             : 
       8             :   use shr_kind_mod, only : r8 => shr_kind_r8
       9             :   use ppgrid,       only : pcols, pver
      10             : 
      11             :   implicit none
      12             :   private
      13             : 
      14             :   public :: cldaero_uptakerate
      15             :   public :: cldaero_conc_t
      16             :   public :: cldaero_allocate
      17             :   public :: cldaero_deallocate
      18             : 
      19             :   type cldaero_conc_t
      20             :      real(r8), pointer :: so4c(:,:)
      21             :      real(r8), pointer :: nh4c(:,:)
      22             :      real(r8), pointer :: no3c(:,:)
      23             :      real(r8), pointer :: xlwc(:,:)
      24             :      real(r8) :: so4_fact
      25             :   end type cldaero_conc_t
      26             : 
      27             : contains
      28             : 
      29             : !----------------------------------------------------------------------------------
      30             : !----------------------------------------------------------------------------------
      31           0 :   function cldaero_allocate( ) result( cldconc )
      32             :     type(cldaero_conc_t), pointer:: cldconc
      33             : 
      34           0 :     allocate( cldconc )
      35           0 :     allocate( cldconc%so4c(pcols,pver) )
      36           0 :     allocate( cldconc%nh4c(pcols,pver) )
      37           0 :     allocate( cldconc%no3c(pcols,pver) )
      38           0 :     allocate( cldconc%xlwc(pcols,pver) )
      39             : 
      40           0 :     cldconc%so4c(:,:) = 0._r8
      41           0 :     cldconc%nh4c(:,:) = 0._r8
      42           0 :     cldconc%no3c(:,:) = 0._r8
      43           0 :     cldconc%xlwc(:,:) = 0._r8
      44           0 :     cldconc%so4_fact  = 2._r8
      45             : 
      46           0 :   end function cldaero_allocate
      47             : 
      48             : !----------------------------------------------------------------------------------
      49             : !----------------------------------------------------------------------------------
      50           0 :   subroutine cldaero_deallocate( cldconc )
      51             :     type(cldaero_conc_t), pointer :: cldconc
      52             : 
      53           0 :     if ( associated(cldconc%so4c) ) then
      54           0 :        deallocate(cldconc%so4c)
      55           0 :        nullify(cldconc%so4c)
      56             :     endif
      57             : 
      58           0 :     if ( associated(cldconc%nh4c) ) then
      59           0 :        deallocate(cldconc%nh4c)
      60           0 :        nullify(cldconc%nh4c)
      61             :     endif
      62             :     
      63           0 :     if ( associated(cldconc%no3c) ) then
      64           0 :        deallocate(cldconc%no3c)
      65           0 :        nullify(cldconc%no3c)
      66             :     endif
      67             : 
      68           0 :     if ( associated(cldconc%xlwc) ) then
      69           0 :        deallocate(cldconc%xlwc)
      70           0 :        nullify(cldconc%xlwc)
      71             :     endif
      72             : 
      73           0 :     deallocate( cldconc )
      74             :     nullify( cldconc )
      75             : 
      76           0 :   end subroutine cldaero_deallocate
      77             : 
      78             : !----------------------------------------------------------------------------------
      79             : ! utility function for cloud-borne aerosols
      80             : !----------------------------------------------------------------------------------
      81             : 
      82           0 :   function cldaero_uptakerate( xl, cldnum, cfact, cldfrc, tfld,  press ) result( uptkrate )
      83             :     use mo_constants, only : pi
      84             : 
      85             :     real(r8), intent(in) :: xl, cldnum, cfact, cldfrc, tfld,  press
      86             : 
      87             :     real(r8) :: uptkrate
      88             : 
      89             :     real(r8) :: &
      90             :          rad_cd, radxnum_cd, num_cd, &
      91             :          gasdiffus, gasspeed, knudsen, &
      92             :          fuchs_sutugin, volx34pi_cd
      93             : 
      94             : !-----------------------------------------------------------------------
      95             : ! compute uptake of h2so4 and msa to cloud water
      96             : !
      97             : ! first-order uptake rate is
      98             : ! 4*pi*(drop radius)*(drop number conc)
      99             : ! *(gas diffusivity)*(fuchs sutugin correction)
     100             : 
     101             : ! num_cd = (drop number conc in 1/cm^3)
     102           0 :         num_cd = 1.0e-3_r8*cldnum*cfact/cldfrc
     103           0 :         num_cd = max( num_cd, 0.0_r8 )
     104             : 
     105             : ! rad_cd = (drop radius in cm), computed from liquid water and drop number,
     106             : ! then bounded by 0.5 and 50.0 micrometers
     107             : ! radxnum_cd = (drop radius)*(drop number conc)
     108             : ! volx34pi_cd = (3/4*pi) * (liquid water volume in cm^3/cm^3)
     109             : 
     110           0 :         volx34pi_cd = xl*0.75_r8/pi
     111             : 
     112             : ! following holds because volx34pi_cd = num_cd*(rad_cd**3)
     113           0 :         radxnum_cd = (volx34pi_cd*num_cd*num_cd)**0.3333333_r8
     114             : 
     115             : ! apply bounds to rad_cd to avoid the occasional unphysical value
     116           0 :         if (radxnum_cd .le. volx34pi_cd*4.0e4_r8) then
     117             :             radxnum_cd = volx34pi_cd*4.0e4_r8
     118             :             rad_cd = 50.0e-4_r8
     119           0 :         else if (radxnum_cd .ge. volx34pi_cd*4.0e8_r8) then
     120             :             radxnum_cd = volx34pi_cd*4.0e8_r8
     121             :             rad_cd = 0.5e-4_r8
     122             :         else
     123           0 :             rad_cd = radxnum_cd/num_cd
     124             :         end if
     125             : 
     126             : ! gasdiffus = h2so4 gas diffusivity from mosaic code (cm^2/s)
     127             : ! (pmid must be Pa)
     128           0 :         gasdiffus = 0.557_r8 * (tfld**1.75_r8) / press
     129             : 
     130             : ! gasspeed = h2so4 gas mean molecular speed from mosaic code (cm/s)
     131           0 :         gasspeed = 1.455e4_r8 * sqrt(tfld/98.0_r8)
     132             : 
     133             : ! knudsen number
     134           0 :         knudsen = 3.0_r8*gasdiffus/(gasspeed*rad_cd)
     135             : 
     136             : ! following assumes accomodation coefficient = 0.65
     137             : ! (Adams & Seinfeld, 2002, JGR, and references therein)
     138             : ! fuchs_sutugin = (0.75*accom*(1. + knudsen)) /
     139             : ! (knudsen*(1.0 + knudsen + 0.283*accom) + 0.75*accom)
     140             :         fuchs_sutugin = (0.4875_r8*(1._r8 + knudsen)) / &
     141           0 :                         (knudsen*(1.184_r8 + knudsen) + 0.4875_r8)
     142             : 
     143             : ! instantaneous uptake rate
     144           0 :         uptkrate = 12.56637_r8*radxnum_cd*gasdiffus*fuchs_sutugin
     145             : 
     146           0 :   end function cldaero_uptakerate
     147             : 
     148           0 : end module cldaero_mod