import cdsapi

c = cdsapi.Client()

c.retrieve(
    'reanalysis-era5-single-levels',
    {
        'product_type': 'reanalysis',
        'variable': 'total_column_water_vapour',
        'year': '2025',
        'month': '10',
        'day': '08',
        'time': '21:00',
        'format': 'netcdf',
    },
    'era5_tcwv_20251008_21.nc'
)