import sys 
import os
import numpy as np
from netCDF4 import Dataset

INDIR='/cluster/shared/noresm/inputdata/atm/cam/tracer_cnst'
FHIST=INDIR + '/' + 'tracer_cnst_halons_3D_L70_1849-2101_CMIP6ensAvg_SSP2-4.5_c190403.nc'
FCLIM=INDIR + '/' + 'tracer_cnst_WACCM6_halons_3DmonthlyL70_1850climoCMIP6piControl001_y21-50avg_c180802.nc' 
FPATH=INDIR + '/' + 'tracer_cnst_halons_3D_L70_1849-2101_CMIP6ensAvg_SSP2-4.5_c190403_LESFMIP-totalO3.nc'
VARS = ['HALONS', 'HO2', 'NO3', 'OH']
NM = 324  

if not(os.path.isfile(FPATH)):
    os.system('cp {:s} {:s}'.format(FHIST,FPATH))

# open files 
nc_hist = Dataset(FHIST, 'r')
nc_clim = Dataset(FCLIM, 'r')
nc = Dataset(FPATH, 'r+', format='NETCDF4_CLASSIC')

# loop over variables 
for field in VARS:    
    data = nc_clim.variables[field][:]
    for year in range(int(NM/12)):
        print(field,year)
        i1 = year*12
        i2 = i1 + 12 
        nc.variables[field][i1:i2,:,:,:] = data 

# close files 
nc_hist.close()
nc_clim.close()
nc.close()