!*==sbsfdi.spg  processed by SPAG 6.70Rc at 15:33 on 10 Dec 2012
!*------------------   SPAG Configuration Options   --------------------
!*--0323,76 000101,-1 000000102011332010100002000000210211210,136 10 --
!*--1100000011112111000000000000,10,10,10,10,10,10,900,100 200000000 --
!*--000000010000000000000,72,72 73,42,38,33 00011112110000100000000  --
!*----------------------------------------------------------------------
!++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
!$Author: joelevin $
!$Date: 2011-03-24 11:33:26 -0500 (Thu, 24 Mar 2011) $
!$Revision: 11724 $
!$HeadURL: https://eweru-dev1.eweru.ksu.edu/svn/code/weps1/branches/WEPS_F90_update/weps.src/src/lib_erosion/sbsfdi.for $
 
      subroutine sbsfdi(slagm,s0ags,slagn,slagx,sldi,sfdi)
      use s_erf
      implicit none
!*--SBSFDI17
!
!*** Start of declarations rewritten by SPAG
!
! Dummy arguments
!
      real :: s0ags,sfdi,slagm,slagn,slagx,sldi
      intent (in) s0ags,slagm,slagn,slagx,sldi
      intent (out) sfdi
!
! Local variables
!
      real :: slt
!
!*** End of declarations rewritten by SPAG
!
 
!     +++ PURPOSE +++
!     calc soil mass fraction (sfdi) < diameter (sldi)
!     given modified lognormal distribution parameters
 
!     +++ ARGUMENT DECLARATIONS +++
 
!     +++  ARGUMENT DEFINITIONS +++
!     slagm - aggregate distribution geometric mean diameter (mm).
!     s0ags - aggregate distribution geometric standard deviation.
!     slagn - aggregate distribution lower limit (mm).
!     slagx - aggregate distribution upper limit (mm).
!     sldi  - soil diameter in distribution (mm)
!     sfdi  - soil mass fraction < sldi
 
!     +++ LOCAL VARIABLES +++
 
!     +++ FUNCTIONS CALLED+++
 
!     +++ END SPECIFICATIONS +++
 
!     calc soil mass < sldi
 
      if (sldi<slagx.AND.sldi>slagn) then
         slt = ((sldi-slagn)*(slagx-slagn))/((slagx-sldi)*slagm)
         sfdi = 0.5*(1+erf(alog(slt)/(sqrt(2.0)*alog(s0ags))))
      else if (sldi>=slagx) then
         sfdi = 1.0
      else
         sfdi = 0.0
      end if
 
      end subroutine sbsfdi