我有一个带有许多尺寸和属性的大型netcdf文件。我想从该文件中提取单个变量，并将其另存为新的netcdf文件，同时保留所有原始元数据。我正在使用xarray。

我使用以下方法打开数据集：

dr=xr.open_dataset("path_to_file")

当我print时，它看起来像这样（为简单起见删除了一些尺寸和元数据：

<xarray.Dataset>
Dimensions:                (Time: 464,bottom_top: 39,bottom_top_stag: 40,snow_layers_stag: 3,snso_layers_stag: 7,soil_layers_stag: 4,south_north: 186,south_north_stag: 187,west_east: 246,west_east_stag: 247)
Coordinates:
    XLAT                   (Time,south_north,west_east) float32 ...
    XLONG                  (Time,west_east) float32 ...
    XTIME                  (Time) datetime64[ns] ...
    XLAT_U                 (Time,west_east_stag) float32 ...
    XLONG_U                (Time,west_east_stag) float32 ...
    XLAT_V                 (Time,south_north_stag,west_east) float32 ...
    XLONG_V                (Time,west_east) float32 ...
Dimensions without coordinates: Time,bottom_top,bottom_top_stag,snow_layers_stag,snso_layers_stag,soil_layers_stag,west_east,west_east_stag
Data variables:
    Times                  (Time) |S19 ...
    UST                    (Time,west_east) float32 ...
    ZNU                    (Time,bottom_top) float32 ...
    ZNW                    (Time,bottom_top_stag) float32 ...
    ZS                     (Time,soil_layers_stag) float32 ...
    DZS                    (Time,soil_layers_stag) float32 ...

Attributes:
    TITLE:                            OUTPUT FROM WRF V3.9 MODEL
    START_DATE:                      2017-10-31_00:00:00
    SIMULATION_START_DATE:           2017-10-01_00:00:00
    WEST-EAST_GRID_DIMENSION:        247
    SOUTH-NORTH_GRID_DIMENSION:      187
    BOTTOM-TOP_GRID_DIMENSION:       40

    HYBRID_OPT:                      -1
    etaC:                            0.0

我只想提取UST，所以我尝试：

dr_u = dr['UST']

但是当我print生成的dr_u时，元数据不见了：

<xarray.Dataset>
Dimensions:  (Time: 464,west_east: 246)
Coordinates:
    XLAT     (Time,west_east) float32 ...
    XLONG    (Time,west_east) float32 ...
    XTIME    (Time) datetime64[ns] ...
Dimensions without coordinates: Time,west_east
Data variables:
    UST      (Time,west_east) float32 ...

我希望能够将所有信息保留在原始文件的Attributes标题下。我知道keep_attrs包中有一个名为xarray的标志，似乎对此很有用，但是我不知道如何在此操作中使用它。