绝大多数nc的数据存在variable中，但也有部分nc数据variable是空的，数据存在其他地方。以下分别对这两类情况进行读取。

情况1：数据在variables中

import netCDF4 as nc

dataset = nc.Dataset('xxx.nc')  # 读取数据
print(dataset.variables.keys())  # 输出所有变量
lon = dataset.variables['longitude'][:].data  # 读取经度
lat = dataset.variables['latitude'][:].data  # 读取维度
time = dataset.variables['time']  # 读取时间
real_time = nc.num2date(time, time.units).data  # 转成时间格式
u10 = dataset.variables['u10'][:].data  # 读取u10风速

情况2：数据不在variable中

参考：https://github.com/acgeospatial/Sentinel-5P/blob/master/Sentinel_5P.ipynb

import numpy as np
import netCDF4 as nc
import pandas as pd
from netCDF4 import Dataset


if __name__ == '__main__':
	fh = Dataset('S5P_OFFL_L2__NO2____20220702T022827_20220702T040957_24441_02_020301_20220703T180630.nc', mode='r')
    print(fh)
    print(fh.file_format)
    print(fh.groups)
    print(fh.groups['PRODUCT'])
    print(fh.groups['PRODUCT'].dimensions)
    print(fh.groups['PRODUCT'].dimensions.keys())
    print(fh.groups['PRODUCT'].dimensions['time'])
    print(fh.groups['METADATA'])
    print(fh.groups['PRODUCT'].variables)
    print(fh.groups['PRODUCT'].variables.keys())

    time = fh.groups['PRODUCT'].variables['time'][:].data
    lon = fh.groups['PRODUCT'].variables['longitude'][:].data
    lat = fh.groups['PRODUCT'].variables['latitude'][:].data
    ntc = fh.groups['PRODUCT'].variables['nitrogendioxide_tropospheric_column'][:].data
    reslut = np.zeros([np.size(lon, 1) * np.size(lon, 2), 3])
    r = 0
    for i in range(np.size(lon, 1)):
        for j in range(np.size(lon, 2)):
            reslut[r, 0:3] = lon[0, i, j], lat[0, i, j], ntc[0, i, j]
            r += 1
    reslut=np.delete(reslut, reslut[:,2]>99999999, 0)
    np.savetxt('S5P_OFFL_L2__NO2____20220702T022827_20220702T040957_24441_02_020301_20220703T180630.txt', reslut,delimiter=',')