!-----------------------------------------------------------------------------
Subroutine Cal_Freq_Monthly(Dr_IDX, Models)
Integer :: imon, imon1, it, ilon, ilat, ireg, ibin, ic, N
Real :: Xmon(Nmon)
Character (Len=*) :: Dr_IDX, Models
Character (Len=3), Parameter :: Mon_Name(Nmon)=(/"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"/)
Do ireg=1, Nreg
   Do ibin=1, Nbin
      Do imon=1, Nmon
         ic=0; N=0
         Do ilon=1, Nlon
            Do ilat=1, Nlat
               if (Int(Reg(ilon,ilat))==ireg) then
                  Do it=1, Ntime
                     if (PDSI(ilon,ilat,it) /= Miss) then
                        imon1=mod(it, Nmon); if (imon1==0) imon1=12
                        if (imon1==imon) then
                           N=N+1
                           if (PDSI(ilon,ilat,it)>=BIN(ibin) .AND. PDSI(ilon,ilat,it)<BIN(ibin+1)) ic=ic+1
                        endif
                     endif
                  Enddo
               endif
            Enddo
         Enddo
         if (N>0) then; Freq_Mon(ireg,ibin,imon) = Real(ic)/Real(N)*100; else; Freq_Mon(ireg,ibin,imon) = Miss; endif
      !   print "(3I3,2F6.2)",ireg, ibin, imon, Freq_Mon(ireg,ibin,imon)
      Enddo
   Enddo
!   print*,Freq_Mon(ireg,1:Nbin,1:Nmon); pause
Enddo
Do ibin=1, Nbin; Xbin(ibin)=(BIN(ibin)+BIN(ibin+1))/2.; Enddo; Do imon=1, Nmon; Xmon(imon)=imon; Enddo
! write to netCDF file:
Fname=trim(Models)//trim(Dr_IDX)//"_Monthly_Reg_Fre_Distribution.nc"
Do ireg=1, Nreg; Xreg(ireg)=ireg; Enddo
!Call wr_ncdf_2d (trim(Fname), Xreg, Xbin, Nreg, Nbin, Freq, "Freq", "Freq_Drought_Index", "-", "Sub-Region", "BIN", Miss)
! wr_ncdf_3d (filenm,lon,lat,t,nlon,nlat,nt, var,var_nm,t_unit, var_long_name, var_unit, lon_nm, lat_nm, t_nm, flag)
Call wr_ncdf_3d (trim(FName), Xreg, Xbin, Xmon, Nreg, Nbin, Nmon, Freq_Mon, "Freq","months since 1980-01-15 00:00:00", &
                              "Mon Freq Distri", "%", "Subregion","BIN","Mon", Miss)
End Subroutine Cal_Freq_Monthly
!--------------------------------------------------------------------------------