1SUBROUTINE cal_helicity (uh, ph, phb, wavg, ims, ime, its, ite)
2  INTEGER, INTENT( IN ) :: ims, ime, its, ite
3  REAL, DIMENSION( ims:ime), INTENT( IN ) :: ph, phb, wavg
4  REAL, DIMENSION( ims:ime), INTENT( INOUT ) :: uh
5  INTEGER :: i
6  REAL :: zu
7  DO i = its, ite
8    zu =  (ph(i ) + phb(i)) + (ph(i-1) + phb(i-1))
9    IF (wavg(i) .GT. 0) THEN
10      uh(i) = uh(i) + zu
11    ENDIF
12  END DO
13END SUBROUTINE cal_helicity
14