SUBROUTINE lwtr(ngrid,coef,lstrong,dup,transm)
      IMPLICIT NONE
      INTEGER ngrid
      REAL coef
      LOGICAL lstrong
      REAL dup(ngrid),transm(ngrid)
      INTEGER ig
      IF(lstrong) THEN
         DO ig=1,ngrid
            transm(ig)=exp(-coef*sqrt(dup(ig)))
         ENDDO
      ELSE
         DO ig=1,ngrid
            transm(ig)=exp(-coef*dup(ig))
         ENDDO
      ENDIF
      RETURN
      END