import cdsapi

c = cdsapi.Client()

c.retrieve(
    'reanalysis-era5-single-levels',
    {
        'product_type': 'reanalysis',
        'variable': 'vertical_integral_of_mass_of_atmosphere',
        'year': '2023',
        'month': '05',
        'day': '12',
        'time': [
            '03:00', '04:00',
        ],
        'area': [
            31, 112, 30,
            113,
        ],
        'format': 'netcdf',
    },
    'download.nc')