Get additional attributes from grib file

[enyfeo]

Hi,
There are some attributes within the grib_file that are being ignored when we open the grib file in cfgrib. Is there a way to augment the list of keys that you would like to include to be converted into the xarray dataset?
They also do not appears in the output using cfgrib.open_file

For example :
dateOfModelVersion = 20181010;

[alexamici]

@enyfeo I'm surprised that this feature had not been requested earlier :)

The reason I didn't implement a way to access the other keys yet is that I couldn't come up with a reasonable API and I fear the implementation would make the open_dataset slower.

I agree this is an important new feature.

[alexamici]

@enyfeo and @EddyCMWF in branch stable/0.9.7.x you can now add the read_keys argument to backend_kwargs with a list of the keys you want to add. Note that all keys MUST have the same value for all messages in a variable. For example to add GRIB_systemNumber:

>>> ds = xr.open_dataset('seas5.grib', engine='cfgrib', backend_kwargs={'read_keys':['systemNumber']})
>>> ds.mx2t24
<xarray.DataArray 'mx2t24' (time: 2, step: 3, latitude: 61, longitude: 120)>
dask.array<shape=(2, 3, 61, 120), dtype=float32, chunksize=(2, 3, 61, 120)>
Coordinates:
    number      int64 ...
  * time        (time) datetime64[ns] 2018-04-01 2018-05-01
  * step        (step) timedelta64[ns] 30 days 31 days 61 days
    surface     int64 ...
  * 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 ... 348.0 351.0 354.0 357.0
    valid_time  (time, step) datetime64[ns] dask.array<shape=(2, 3), chunksize=(2, 3)>
Attributes:
    GRIB_paramId:                             51
    GRIB_shortName:                           mx2t24
    ...
    GRIB_systemNumber:                        5
    long_name:                                Maximum temperature at 2 metres...
    units:                                    K

Note that the feature is experimental.

[enyfeo]

Hi, Looks great,
Will check it out.

[alexamici]

I released version 0.9.7.2 with the feature.

[edupenabad]

I have just tried this one with both 0.9.7.2 and 0.9.7.3 and I haven't managed to get the systemNumber keyword value:

In [3]: ds=xr.open_dataset('seas5_t2m_6h.grib',engine='cfgrib',backend_kwargs={'read_keys':['systemNumber']})                                           

In [4]: ds                                                                                                                                              
Out[4]: 
<xarray.Dataset>
Dimensions:     (latitude: 181, longitude: 360, step: 16, time: 2)
Coordinates:
    number      int64 ...
  * time        (time) datetime64[ns] 2019-10-01 2019-11-01
  * step        (step) timedelta64[ns] 0 days 06:00:00 ... 4 days 00:00:00
    surface     int64 ...
  * latitude    (latitude) float64 90.0 89.0 88.0 87.0 ... -88.0 -89.0 -90.0
  * longitude   (longitude) float64 0.0 1.0 2.0 3.0 ... 356.0 357.0 358.0 359.0
    valid_time  (time, step) datetime64[ns] ...
Data variables:
    t2m         (time, step, latitude, longitude) float32 ...
Attributes:
    GRIB_edition:            1
    GRIB_centre:             ecmf
    GRIB_centreDescription:  European Centre for Medium-Range Weather Forecasts
    GRIB_subCentre:          0
    Conventions:             CF-1.7
    institution:             European Centre for Medium-Range Weather Forecasts
    history:                 2019-11-15T17:55:12 GRIB to CDM+CF via cfgrib-0....

In [5]: xr.__version__                                                                                                                                  
Out[5]: '0.14.0'

In [6]: cfgrib.__version__                                                                                                                              
Out[6]: '0.9.7.2'

Do you have any suggestion on what I might be doing wrong?

[alexamici]

@edupenabad additional keys are added to the variable attrs, not to the global ones, check out the attrs of ds.t2m

[enyfeo]

Hi Eduardo, I did try this and saw it working. If I recall correctly the systemNumber would show if you look at the variable. So try ds.t2m

…

On Fri, 15 Nov 2019 at 18:02, Eduardo Penabad Ramos < ***@***.***> wrote: I have just tried this one with both 0.9.7.2 and 0.9.7.3 and I haven't managed to get the systemNumber keyword value: In [3]: ds=xr.open_dataset('seas5_t2m_6h.grib',engine='cfgrib',backend_kwargs={'read_keys':['systemNumber']}) In [4]: ds Out[4]: <xarray.Dataset> Dimensions: (latitude: 181, longitude: 360, step: 16, time: 2) Coordinates: number int64 ... * time (time) datetime64[ns] 2019-10-01 2019-11-01 * step (step) timedelta64[ns] 0 days 06:00:00 ... 4 days 00:00:00 surface int64 ... * latitude (latitude) float64 90.0 89.0 88.0 87.0 ... -88.0 -89.0 -90.0 * longitude (longitude) float64 0.0 1.0 2.0 3.0 ... 356.0 357.0 358.0 359.0 valid_time (time, step) datetime64[ns] ... Data variables: t2m (time, step, latitude, longitude) float32 ... Attributes: GRIB_edition: 1 GRIB_centre: ecmf GRIB_centreDescription: European Centre for Medium-Range Weather Forecasts GRIB_subCentre: 0 Conventions: CF-1.7 institution: European Centre for Medium-Range Weather Forecasts history: 2019-11-15T17:55:12 GRIB to CDM+CF via cfgrib-0.... In [5]: xr.__version__ Out[5]: '0.14.0' In [6]: cfgrib.__version__ Out[6]: '0.9.7.2' Do you have any suggestion on what I might be doing wrong? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#89?email_source=notifications&email_token=AGW3QPTZJ4ZXN6GRCBNHOGTQT3P4JA5CNFSM4HVWN3T2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEEGHTUY#issuecomment-554465747>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AGW3QPQDEQNLQFDOGOOFUADQT3P4JANCNFSM4HVWN3TQ> .

[edupenabad]

Thanks!
My fault! I just got confused when having some GRIB keywords in the global attributes and not others.