source: LMDZ6/trunk/libf/phylmd/cosp/pf_to_mr.f90

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! $Revision: 23 $, $Date: 2011-03-31 15:41:37 +0200 (jeu. 31 mars 2011) $
! $URL: http://cfmip-obs-sim.googlecode.com/svn/stable/v1.4.0/llnl/pf_to_mr.f $
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subroutine pf_to_mr(npoints,nlev,ncol,rain_ls,snow_ls,grpl_ls, &
        rain_cv,snow_cv,prec_frac, &
        p,t,mx_rain_ls,mx_snow_ls,mx_grpl_ls, &
        mx_rain_cv,mx_snow_cv)


  implicit none

  INTEGER :: npoints       !  number of model points in the horizontal
  INTEGER :: nlev          !  number of model levels in column
  INTEGER :: ncol          !  number of subcolumns

  INTEGER :: j,ilev,ibox

  REAL :: rain_ls(npoints,nlev),snow_ls(npoints,nlev) ! large-scale precip. flux
  REAL :: grpl_ls(npoints,nlev)
  REAL :: rain_cv(npoints,nlev),snow_cv(npoints,nlev) ! convective precip. flux

  REAL :: prec_frac(npoints,ncol,nlev) ! 0 -> clear sky
                                    ! ! 1 -> LS precipitation
                                    ! ! 2 -> CONV precipitation
                                    ! ! 3 -> both
  REAL :: mx_rain_ls(npoints,ncol,nlev),mx_snow_ls(npoints,ncol,nlev)
  REAL :: mx_grpl_ls(npoints,ncol,nlev)
  REAL :: mx_rain_cv(npoints,ncol,nlev),mx_snow_cv(npoints,ncol,nlev)
  REAL :: p(npoints,nlev),t(npoints,nlev)
  REAL :: ar,as,ag,br,bs,bg,nr,ns,ng,rho0,rhor,rhos,rhog,rho
  REAL :: term1r,term1s,term1g,term2r,term2s,term2g,term3
  REAL :: term4r_ls,term4s_ls,term4g_ls,term4r_cv,term4s_cv
  REAL :: term1x2r,term1x2s,term1x2g,t123r,t123s,t123g

  ! ! method from Khairoutdinov and Randall (2003 JAS)

  ! ! --- List of constants from Appendix B
  ! ! Constant in fall speed formula
  ar=842.
  as=4.84
  ag=94.5
  ! ! Exponent in fall speed formula
  br=0.8
  bs=0.25
  bg=0.5
  ! ! Intercept parameter
  nr=8.*1000.*1000.
  ns=3.*1000.*1000.
  ng=4.*1000.*1000.
  ! ! Densities for air and hydrometeors
  rho0=1.29
  rhor=1000.
  rhos=100.
  rhog=400.
  ! ! Term 1 of Eq. (A19).
  term1r=ar*17.8379/6.
  term1s=as*8.28508/6.
  term1g=ag*11.6317/6.
  ! ! Term 2 of Eq. (A19).
  term2r=(3.14159265*rhor*nr)**(-br/4.)
  term2s=(3.14159265*rhos*ns)**(-bs/4.)
  term2g=(3.14159265*rhog*ng)**(-bg/4.)

  term1x2r=term1r*term2r
  term1x2s=term1s*term2s
  term1x2g=term1g*term2g
  do ilev=1,nlev
    do j=1,npoints
        rho=p(j,ilev)/(287.05*t(j,ilev))
        term3=(rho0/rho)**0.5
        ! ! Term 4 of Eq. (A19).
        t123r=term1x2r*term3
        t123s=term1x2s*term3
        t123g=term1x2g*term3
        term4r_ls=rain_ls(j,ilev)/(t123r)
        term4s_ls=snow_ls(j,ilev)/(t123s)
        term4g_ls=grpl_ls(j,ilev)/(t123g)
        term4r_cv=rain_cv(j,ilev)/(t123r)
        term4s_cv=snow_cv(j,ilev)/(t123s)
        do ibox=1,ncol
            mx_rain_ls(j,ibox,ilev)=0.
            mx_snow_ls(j,ibox,ilev)=0.
            mx_grpl_ls(j,ibox,ilev)=0.
            mx_rain_cv(j,ibox,ilev)=0.
            mx_snow_cv(j,ibox,ilev)=0.
            if ((prec_frac(j,ibox,ilev) .eq. 1.) .or. &
                  (prec_frac(j,ibox,ilev) .eq. 3.)) then
                mx_rain_ls(j,ibox,ilev)= &
                      (term4r_ls**(1./(1.+br/4.)))/rho
                mx_snow_ls(j,ibox,ilev)= &
                      (term4s_ls**(1./(1.+bs/4.)))/rho
                mx_grpl_ls(j,ibox,ilev)= &
                      (term4g_ls**(1./(1.+bg/4.)))/rho
            endif
            if ((prec_frac(j,ibox,ilev) .eq. 2.) .or. &
                  (prec_frac(j,ibox,ilev) .eq. 3.)) then
                mx_rain_cv(j,ibox,ilev)= &
                      (term4r_cv**(1./(1.+br/4.)))/rho
                mx_snow_cv(j,ibox,ilev)= &
                      (term4s_cv**(1./(1.+bs/4.)))/rho
            endif
        enddo ! loop over ncol
    enddo ! loop over npoints
  enddo ! loop over nlev

end subroutine pf_to_mr