import cdsapi

c = cdsapi.Client()

c.retrieve(
    'cams-global-atmospheric-composition-forecasts-test',
    {
        'date':          '2023-04-01/2023-04-10',
        'type':          'forecast',
        'format':        'netcdf_zip',
        'model_level':   '137',                    # Lowest model level only
        'variable':    [ 'biogenic_secondary_organic_aerosol_mass_mixing_ratio',
                         'anthropogenic_secondary_organic_aerosol_mass_mixing_ratio',
                         'glyoxal',
                         'secondary_organic_aerosol_optical_depth_550nm',
                         'total_column_glyoxal' ], # See other variables at:
        'time':          '00:00',                  # https://ads.atmosphere.copernicus.eu/cdsapp#!/dataset/cams-global-atmospheric-composition-forecasts?tab=form
        'leadtime_hour': [h for h in range(0,25,3)],
        'area':          [70, -35, 35, 60]         # [N,EW,S,WE] Europe area boundaries
    },
    '/tmp/cams_test_20230401_10.nc.zip')