远程访问NASA MERRA-2数据集时遇权限错误求助

我按照NASA官方指南步骤从公共数据库获取PM2.5数据，已在主目录创建.netrc、.urs_cookies、.dodsrc三个文件，且拥有NASA账号。执行以下代码时出现权限相关错误：

ds = xr.open_dataset(URL1).sel(lat=slice(lat1,lat2),lon=slice(lon1,lon2),time=slice(time1,time2))

错误信息如下：

syntax error, unexpected WORD_WORD, expecting SCAN_ATTR or SCAN_DATASET or SCAN_ERROR context: HTTP^ Basic: Access denied. Output exceeds the size limit. Open the full output data in a text editor
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/xarray/backends/file_manager.py:210, in CachingFileManager._acquire_with_cache_info(self, needs_lock)
    209 try:
---> 210     file = self._cache[self._key]
    211 except KeyError:

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/xarray/backends/lru_cache.py:56, in LRUCache.__getitem__(self, key)
     55 with self._lock:
---> 56     value = self._cache[key]
     57     self._cache.move_to_end(key)

KeyError: [, ('https://goldsmr4.gesdisc.eosdis.nasa.gov/thredds/dodsC/MERRA2_MONTHLY_aggregation/M2TMNXAER.5.12.4_Aggregation.ncml',), 'r', (('clobber', True), ('diskless', False), ('format', 'NETCDF4'), ('persist', False)), '0847945a-4bb6-4085-8032-785c28de3f80']

During handling of the above exception, another exception occurred:

OSError                                   Traceback (most recent call last)
Input In [3], in ()
     14 time2 = datetime(2019,12,1,0,30,0) # end date
     16 # Read the data for the specified latitude/longitude and date range
---> 17 ds = xr.open_dataset(URL1).sel(lat=slice(lat1,lat2),lon=slice(lon1,lon2),time=slice(time1,time2))

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/xarray/backends/api.py:526, in open_dataset(filename_or_obj, engine, chunks, cache, decode_cf, mask_and_scale, decode_times, decode_timedelta, use_cftime, concat_characters, decode_coords, drop_variables, inline_array, backend_kwargs, **kwargs)
    514 decoders = _resolve_decoders_kwargs(
    515     decode_cf, ...
File src/netCDF4/_netCDF4.pyx:2449, in netCDF4._netCDF4.Dataset.__init__()

File src/netCDF4/_netCDF4.pyx:2012, in netCDF4._netCDF4._ensure_nc_success()

OSError: [Errno -77] NetCDF: Access failure: 'https://goldsmr4.gesdisc.eosdis.nasa.gov/thredds/dodsC
/MERRA2_MONTHLY_aggregation/M2TMNXAER.5.12.4_Aggregation.ncml'

排查方向 #

1. 身份验证文件配置问题

• 检查.netrc文件内容格式是否正确，必须为：

  machine urs.earthdata.nasa.gov login YOUR_NASA_USERNAME password YOUR_NASA_PASSWORD
  

  替换实际账号密码，同时设置文件权限为600（仅当前用户可读可写）：

  chmod 600 ~/.netrc
  

• 确认.dodsrc文件包含关键配置，替换YOUR_USERNAME为实际用户名：

  HTTP.COOKIEJAR=/Users/YOUR_USERNAME/.urs_cookies
  HTTP.NETRC=/Users/YOUR_USERNAME/.netrc
  HTTP.SSL.CERTIFICATE=/etc/pki/tls/certs/ca-bundle.crt
  

2. 账号与数据权限

• 登录NASA EarthData账号，确认已完成MERRA-2数据集的授权流程（部分数据集需手动授权访问）。
• 手动访问报错中的URL，用浏览器登录账号后验证是否能正常打开，排查账号锁定或权限缺失问题。

3. 依赖库与环境配置

• 更新netCDF4和xarray到最新版本，旧版本可能存在身份验证兼容问题：

  pip install --upgrade netCDF4 xarray
  

• 检查环境变量是否加载.dodsrc配置：

  echo $DODS_CONFIG
  

  若未输出正确路径，手动设置环境变量：

  export DODS_CONFIG=~/.dodsrc
  

4. 网络与代理问题

• 若使用代理，在.dodsrc中添加代理配置：

  HTTP.PROXY=your_proxy_url:port
  HTTP.PROXYUSER=proxy_username
  HTTP.PROXYPASS=proxy_password
  

• 用curl验证身份连通性：

  curl -n https://urs.earthdata.nasa.gov
  

  返回登录页面或成功响应则验证正常，否则检查账号密码正确性。

内容的提问来源于stack exchange，提问作者futur3boy