parameter (nx=144, ny=73, ntot= 9855, nt= 256)
	parameter (ii=144, jj=13 )
	real olr(nx,ny,nt), c_olr(ii,jj,nt), sym(ii,jj,nt), asy(ii,jj,nt)
        real com(ii,jj,nt)
	real undef
	data undef /-999./

	open (1,
     *file='/home/enver/work/programs/MJOWG/msd/level_1/'//
     * 'u200_n1/data/'//
     * 'daily.anom.19790101_20051231.gdat',
     *  form='unformatted',access='direct',recl=nx*ny*4,
     *  status='old')

	open (11,
     *file='/home/enver/work/programs/MJOWG/msd/level_2/'//
     * 'coh2/u200_n1/data/'//
     * 'seg256_over206_sym_asy.gdat',
     *  form='unformatted',access='direct',recl=ii*jj*4,
     *  status='unknown')

	iseg=0
	irec=0
	nskip=0
	overlap=206

	it1= nskip+1
	it2= it1+nt-1

10	continue	
	jrec=0
	do it=it1,it2
	 jrec=jrec+1
	 read (1,rec=it) ((olr(i,j,jrec),i=1,nx),j=1,ny)
	enddo

c -999. check for TRMM
        do jr = 1, jrec
         do j = 1, jj
         do i = 1, nx 
           j1 = j+30
          if (olr(i,j1,jr).eq.undef) then
           print*,'-999.'
            olr(i,j1,jr) = 0.5*(olr(i,j1,jr-1)+olr(i,j1,jr+1))
          endif
         enddo
         enddo
        enddo

	iseg=iseg+1
	print*,iseg,'=iseg'

! sym & asy
	do k=1,nt
	do j=1,jj
          j1 = j+30
          j2 = ny+1-j1

	do i=1,nx
	 sym(i,j,k) = 0.5*(olr(i,j1,k)+olr(i,j2,k))
	 asy(i,j,k) = 0.5*(olr(i,j1,k)-olr(i,j2,k))
	enddo ! i

	enddo ! j
	enddo ! k

! detrend	
        call detrend (sym,nx,jj,nt)
        call detrend (asy,nx,jj,nt)
! tapering both ends to zero
c      apply a tapering to the first and last 5 days by multiplication
c      by a segment of the cosine curve so that the ends of the series
c      taper towards zero (mean has been removed anyway)!
        call tapertozero (sym,nx,jj,nt,1,nt,5)
        call tapertozero (asy,nx,jj,nt,1,nt,5)
! write_seg

	do it=1,nt
	 irec=irec+1

         do j = 1, jj
         do i = 1, nx
           if (j.ge.1.and.j.le.(jj/2+1)) then
            com(i,j,it) = sym(i,j,it)
           else
            com(i,j,it) = asy(i,j,it)
           endif
         enddo
         enddo

	 write (11,rec=irec) ((com(i,j,it),i=1,ii),j=1,jj)
	enddo
	
	it1=it2-overlap+1
	it2=it1+nt-1
	if(it2.gt.ntot) goto 20
	goto 10

20     continue
	print*,iseg,'= total 256-day segments'
   
	stop
	end
c-----------------------------------------------------------------------
      subroutine detrend (tmp2,nl,nlat,nt)
      implicit none
      integer NL,nlat,NT,n,m,t, tmean,sum
      real tmp2(NL,nlat,NT),y(NT)
      real a, b
        do 10 n=1,nl
        do 10 m=1,nlat
         do 20 t=1,nt
           y(t)=tmp2(n,m,t)
  20     continue
        tmean=sum(y,nt)
         call reg (y,nt,a,b)
         do 30 t=1,nt
           tmp2(n,m,t)=tmp2(n,m,t)-(a+b*float(t-1))
c           tmp2(n,m,t)=tmp2(n,m,t)-tmean/float(nt)
  30     continue
  10  continue
      return
      end
c-----------------------------------------------------------------------
      subroutine reg (y,n,a,b)
      implicit none
      integer i,n
      real a,b,xbar,ybar,sum
      real y(n)
      real xy(n),xx(n)
c
      xbar=n*(n+1)/2.
      ybar=sum (y,n)/float(n)
      do 100 i=1,n
         xy(i)=(i-xbar)*(y(i)-ybar)
         xx(i)=(i-xbar)**2
100   continue
      b=sum(xy,n)/sum(xx,n)
      a=ybar-b*xbar
c
      return
      end
c-----------------------------------------------------------------------
      function sum (x,n)
      implicit none
      integer n,i
      real x(n),sumx, sum
      sumx=0.
      do 100 i=1,n
       sumx=sumx+x(i)
100   continue
      sum=sumx
      return
      end
c-----------------------------------------------------------------
       subroutine tapertozero(ts,imax,jmax,N,nmi,nn,tp)
       implicit none

c "taper" the first and last 'tp' members of 'ts' by multiplication by
c a segment of the cosine curve so that the ends of the series
c taper toward zero. This satisfies the
c 19790101_20051231ic requirement of the FFT.
c Only the data from nmi to nmi+nn-1 is deemed useful, and
c the rest is set to zero. (There are nn points of useful data)
       integer i,j,N,tp,nmi,nn, imax, jmax, ii, jj
       real Pi,ts(imax,jmax,N)
       parameter (Pi=3.1415926)   !tp is number to taper on each end.

       if (N.lt.25.or.nn.lt.25) then
        print*,'No use doing the tapering if less than 25 values!'
        STOP
       endif
       if (nmi+nn-1.gt.N) then
        print*,'ERROR as nmi+nn-1 > N'
        STOP
       endif

       do jj = 1, jmax
       do ii = 1, imax

       do i=1,N
        j=i-nmi+1
        if (j.le.0.or.j.gt.nn) then
         ts(ii,jj,i)=0.
        elseif (j.le.tp) then
         ts(ii,jj,i)= ts(ii,jj,i)*.5*(1.-COS((j-1)*Pi/float(tp)))
        elseif (j.gt.(nn-tp).and.j.le.nn) then
         ts(ii,jj,i)= ts(ii,jj,i)*.5*(1.-COS((nn-j)*Pi/float(tp)))
        else
         ts(ii,jj,i)= ts(ii,jj,i)
        endif
       enddo

       enddo
       enddo

       return
       end