!*==sbpm10.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/sbpm10.for $
!**********************************************************************
!     subroutine sbpm10         ver 1  3-4-2005
!**********************************************************************
      subroutine sbpm10(seags,secr,sfcla,sfsan,awzypt,&canag,cancr,     &
                      & sf10an,sf10en,sf10bk)
      implicit none
!*--SBPM1018
!
!*** Start of declarations rewritten by SPAG
!
! Dummy arguments
!
      real :: awzypt,canag,cancr,seags,secr,sf10an,sf10bk,sf10en,sfcla, &
            & sfsan
      intent (in) awzypt,seags,secr,sfcla,sfsan
      intent (out) cancr,sf10an,sf10bk,sf10en
      intent (inout) canag
!
! Local variables
!
      real :: cla,lnc,ppt,ratio,sfsil
!
!*** End of declarations rewritten by SPAG
!
!
!     + + + PURPOSE + + +
!     Calculates abrasion coefficients and PM10 fractions in
!       sources of suspended soil
!
!     + + + ARGUMENT DECLARTAIONS + + +
!
!     + + + ARGUMENT DEFINITIONS + + +
!     seags  = aggreg. stability [Ln(J/Kg)]
!     secr   = crust stabitlity [Ln(J/Kg)]
!     sfcla  = soil surface fraction clay
!     sfsan  = soil surface faction sand
!     awzypt = annual average precipitation (mm)
!     canag  = coefficent of abrasion of aggregates (1/m)
!     cancr  = coefficient of abrasion of crust (1/m)
!     sf10an = fraction pm10 in abraded supension size soil
!     sf10en = fraction pm10 in emitted suspension size soil
!     sf10bk = fraction pm10 in breakage from saltion size soil
!
!     + + + LOCAL VARIABLES + + +
!
!     + + + LOCAL VARIABLE DEFIINTIONS + + +
!       ratio = silt/clay^2
!       cla   = fraction clay with restricted range
!       lnc   = alog (cla)
!       sfsil = soil fraction silt
!       ppt   = annual average precip restricted to 100-800 mm
!     + + +  END SPECIFICATIONS + + +
!
!       calc. abrasion coefficients
      canag = exp(-2.07-0.077*seags**2.5-0.119*alog(seags))
      if (secr==0.0) then        ! No crust stability value specified
         cancr = 0.0
         write (0,*) 'Warning:  Crust stability value is set to zero'
      else
         cancr = exp(-2.07-0.077*secr**2.5-0.119*alog(secr))
      end if
!
!       calc. pm10 fractions in suspended soil
      sf10an = 0.0116 + 0.00025/(canag+0.001)
!
      sfsil = 1 - sfsan - sfcla
      ratio = sfsil/(sfcla+0.0001)**2
      ratio = min(300.0,ratio)
      sf10en = 0.0067 + 0.0000487*ratio - 0.0000044*awzypt
!
      cla = min(0.42,max(0.017,sfcla))    !restrict clay range
      lnc = alog(cla)
      ppt = min(800.0,max(100.0,awzypt))      !restrict precip range
      sf10bk = -0.201 - (0.52+(0.422+(0.1395+0.0156*lnc)*lnc)*lnc)      &
             & *lnc& + 0.131*exp(-ppt/175.6)
!
      end subroutine sbpm10