Please add support for GRIB files via ECMWF cfgrib / ecCodes

[alexamici]

The cfgrib project offers to open a GRIB file as an xarray.Dataset:

>>> import cfgrib
>>> cfgrib.open_dataset('era5-levels-members.grib')
<xarray.Dataset>
Dimensions:       (air_pressure: 2, latitude: 61, longitude: 120, number: 10, time: 4)
Coordinates:
  * number        (number) int64 0 1 2 3 4 5 6 7 8 9
  * time          (time) datetime64[ns] 2017-01-01 ... 2017-01-02T12:00:00
    step          timedelta64[ns] ...
  * air_pressure  (air_pressure) float64 850.0 500.0
  * latitude      (latitude) float64 90.0 87.0 84.0 81.0 ... -84.0 -87.0 -90.0
  * longitude     (longitude) float64 0.0 3.0 6.0 9.0 ... 351.0 354.0 357.0
    valid_time    (time) datetime64[ns] ...
Data variables:
    z             (number, time, air_pressure, latitude, longitude) float32 ...
    t             (number, time, air_pressure, latitude, longitude) float32 ...
Attributes:
    GRIB_edition:            1
    GRIB_centre:             ecmf
    GRIB_centreDescription:  European Centre for Medium-Range Weather Forecasts
    GRIB_subCentre:          0
    history:                 GRIB to CDM+CF via cfgrib-0.9.../ecCodes-2...

It would be very helpful to have a backend for it distributed with xarray to be selected via the engine keyword argument:

>>> import xarray as xr
>>> xr.open_dataset('era5-levels-members.grib', engine='cfgrib')
<xarray.Dataset>
Dimensions:       (air_pressure: 2, latitude: 61, longitude: 120, number: 10, time: 4)
Coordinates:
  * number        (number) int64 0 1 2 3 4 5 6 7 8 9
  * time          (time) datetime64[ns] 2017-01-01 ... 2017-01-02T12:00:00
    step          timedelta64[ns] ...
  * air_pressure  (air_pressure) float64 850.0 500.0
  * latitude      (latitude) float64 90.0 87.0 84.0 81.0 ... -84.0 -87.0 -90.0
  * longitude     (longitude) float64 0.0 3.0 6.0 9.0 ... 351.0 354.0 357.0
    valid_time    (time) datetime64[ns] ...
Data variables:
    z             (number, time, air_pressure, latitude, longitude) float32 ...
    t             (number, time, air_pressure, latitude, longitude) float32 ...
Attributes:
    GRIB_edition:            1
    GRIB_centre:             ecmf
    GRIB_centreDescription:  European Centre for Medium-Range Weather Forecasts
    GRIB_subCentre:          0
    history:                 GRIB to CDM+CF via cfgrib-0.9.../ecCodes-2...

cc @StephanSiemen @iainrussell

[alexamici]

Great! @shoyer you can close the issue as resolved for me.

[jhamman]

Thanks @alexamici for this contribution!