c***********************************************************************
c*     subroutine sbwind
c***********************************************************************
      subroutine sbwind
     i (vus, vust, vusp, wustfl,
     o aicsr)
c
c     +++ PURPOSE +++
c     To initialize a soil friction velocity on each grid point
c     and modify it for barriers and hills;
c     To initialize en thresh. and tp thresh. fr. velocites on grid;
c     To calculate max ratios of friction velocity to threshold
c     friction velocity
c     To update only friction vel. when 'update' of sfc. =0
c
c     +++ ARGUMENT DECLARATIONS +++
      integer  wustfl

      real vus, vust, vusp
      real aicsr
c     +++ ARGUMENT DEFINITIONS +++
c     icsr - index of current subregion.
c     wustfl - flag to signal surface was updated
c     wur  - ratio of current to ref wind speed( wu at last update)
c     vus  - uncorrected subregion soil friction velocity (m/s).
c     vust - subrgion soil threshold friction velocity (m/s).
c     wusp - subregion soil threshold friction vel. trans. cap. (m/s)
c     aicsr- max ratio of friction velocity to thresh. friction vel.
c     imax - no. grid intervals in x-direction.
c     jmax - no. grid intervals in y-direction.
c     ix   - grid interval in x-direction(m).
c     jy   - grid interval in y-direction(m).
c     wus  - soil friction velocity at grid points corrected for
c            hills and barriers (m/s).
c     wust - threshold fr. vel. for en. at grid points
c     wusp - threshold fr. vel. for trans. cap. at grid points
c
c     + + + GLOBAL COMMON BLOCKS + + +
*$noreference
      include  'p1werm.inc'
      include  'm1geo.inc'
c
c     + + + LOCAL COMMON BLOCKS + + +
      include  'erosion/m2geo.inc'
      include  'erosion/w2wind.inc'
      include  'erosion/e2grid.inc'
      include  'erosion/e3grid.inc'
c
*$reference
c     +++ LOCAL VARIABLES +++
      integer i,j
c
       real*4 at
c
c     + + + END SPECIFICATIONS + + +
c
      aicsr = 0.

      do 50 i = 1, imax
      do 45 j = 1, jmax

      if (wustfl .eq. 0) then
        wus(i,j) = vus
        at = wus(i,j)/vust
        aicsr = amax1(aicsr, at)

      else
        wus(i,j) = vus
        wust(i,j)= vust
        wusp(i,j)= vusp
        at = wus(i,j)/vust
        aicsr = amax1(aicsr, at)

      endif
c
c     correct friction velocity for hills
c      if (nhill .ne. 0 ) then
c           wus(i,j) = wus(i,j) * w0hill(i,j,kbr)
c        endif
c
c     correct friction velocity for barriers
      if (nbr .ne. 0 ) then
            wus(i,j) =wus (i,j) * w0br (i,j,kbr)
      endif
   45 continue
   50 continue
c
      return
      end
c++++ +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++