
      subroutine NLDIFSW
     I  (  UM2   , WM2, 
     M     DTQDNL,
     D     NXB   , NZB  )
!-----------------------------------------------------------------------
      implicit real*8 ( a-h, o-z )
!-----------------------------------------------------------------------

      dimension
     \     UM2  ( -2:NXB, -2:NZB ),
     \     WM2  ( -2:NXB, -2:NZB ),
     \     DTQDNL ( -2:NXB, -2:NZB )

!-----------------------------------------------------------------------

      VABS0 = 1.0D0

      do iz = -2, NZB
         do ix = -2, NXB
            vabs = SQRT( UM2(ix,iz)**2 + WM2(ix,iz)**2 )
            DTQDNL(ix,iz) = DTQDNL(ix,iz) * 
     \           MIN( 1.0D0, ( VABS/VABS0 )**5.0 )
         end do
      end do

      return

      end
