Use NetCDF

   Real, Parameter :: Miss=-99.0
   Real, Parameter :: ec_miss=-32767.0, obs_miss=-9999.0
   Integer :: Nlon, Nlat, ilon, ilat, Nt
   Real, Allocatable :: Lon(:), Lat(:), Mask(:,:), X2d(:,:), X3d(:,:,:), xtime(:)
   Character (Len=255) :: Fname

   Fname="/home/tanpv/Progs/S2S_4Giang/Data/CHIRPS_Giang/chirps_2017-03-02.nc"
   Call rd_ncdf_3d (Fname,lon,lat,xtime,nlon,nlat,Nt,X3d,"precip") 
   Where (X3d==obs_miss) X3d=Miss
   Allocate (X2d(nlon,nlat),Mask(nlon,nlat))
   X2d(:,:) = X3d(:,:,20)
   Do ilon=1,Nlon
      Do ilat=1,Nlat
         if (X2d(ilon,ilat)>=0) then
            Mask(ilon,ilat) = 1
         else
            Mask(ilon,ilat) = Miss
         endif
      Enddo
   Enddo
   Fname="/home/tanpv/Progs/S2S_4Giang/Data/Mask_Giang.nc"
   Call wr_ncdf_2d (Fname,lon,lat,nlon,nlat,Mask,"land","Landmask for Red River Basin","-","lon","lat",Miss)
 
   CONTAINS
   Include "/home/tanpv/Mylibs/sub_rd_ncdf_Tan.F90"
   Include "/home/tanpv/Mylibs/sub_wr_ncdf_Tan.F90"
   END