'fast_Herbie_xarray' unable to grab 'gribfile_projection'

[akumler]

Hello,

I am downloading multiple forecasts using fast_Herbie_xarray(), and so far I have successfully used it to download HRRR data. Now I am attempting to grab GFS data, but I get the error:

Traceback (most recent call last):

  File "/var/folders/r9/_yc_yf6d5k38whv10mx_tzkd15bsjb/T/ipykernel_20173/4263070027.py", line 4, in <cell line: 1>
    ds = fast_Herbie_xarray(DATES=total_date_range, fxx=fxx, model=json_file[mod]['model_name'],

  File "/Users/akumler/miniconda3/envs/naerm/lib/python3.8/site-packages/herbie/tools.py", line 247, in fast_Herbie_xarray
    ds["gribfile_projection"] = ds.gribfile_projection[0][0]

  File "/Users/akumler/miniconda3/envs/naerm/lib/python3.8/site-packages/xarray/core/common.py", line 239, in __getattr__
    raise AttributeError(

AttributeError: 'Dataset' object has no attribute 'gribfile_projection'

Looking at some example GFS data via xarray, we see that 'gribfile_projection' is a data variable, but not an attribute.

<xarray.Dataset>
Dimensions:              (latitude: 721, longitude: 1440)
Coordinates:
    time                 datetime64[ns] 2021-07-11
    step                 timedelta64[ns] 00:00:00
    heightAboveGround    float64 2.0
  * latitude             (latitude) float64 90.0 89.75 89.5 ... -89.75 -90.0
  * longitude            (longitude) float64 0.0 0.25 0.5 ... 359.2 359.5 359.8
    valid_time           datetime64[ns] 2021-07-11
Data variables:
    t2m                  (latitude, longitude) float32 273.7 273.7 ... 221.6
    aptmp                (latitude, longitude) float32 269.0 269.0 ... 202.0
    gribfile_projection  object None
Attributes:
    GRIB_edition:            2
    GRIB_centre:             kwbc
    GRIB_centreDescription:  US National Weather Service - NCEP
    GRIB_subCentre:          0
    Conventions:             CF-1.7
    institution:             US National Weather Service - NCEP
    model:                   gfs
    product:                 pgrb2.0p25
    description:             Global Forecast System
    remote_grib:             https://noaa-gfs-bdp-pds.s3.amazonaws.com/gfs.20...
    local_grib:              /Users/akumler/data/gfs/20210711/subset_446869af...
    searchString:            TMP:2 m above

Digging deeper, it appears there is a projection, but the way that 'fast_Herbie_xarray' is currently set up doesn't recognize this? Am I missing something? Thanks!

x.gribfile_projection
Out[25]: 
<xarray.DataArray 'gribfile_projection' ()>
array(None, dtype=object)
Coordinates:
    time               datetime64[ns] 2021-07-11
    step               timedelta64[ns] 00:00:00
    heightAboveGround  float64 2.0
    valid_time         datetime64[ns] 2021-07-11
Attributes:
    crs_wkt:                      GEOGCRS["unknown",DATUM["unknown",ELLIPSOID...
    semi_major_axis:              6371229.0
    semi_minor_axis:              6371229.0
    inverse_flattening:           0.0
    reference_ellipsoid_name:     unknown
    longitude_of_prime_meridian:  0.0
    prime_meridian_name:          Greenwich
    geographic_crs_name:          unknown
    grid_mapping_name:            latitude_longitude
    long_name:                    GFS model grid projection

[blaylockbk]

Hi @akumler, Thanks for pointing out this issue. I started writing a new FastHerbie() class that might not have this problem. I haven't found time to add documentation for it yet, but here is a notebook that shows how to use the FastHerbie() class... https://github.com/blaylockbk/Herbie/blob/main/notebooks/New_FastHerbie.ipynb

If that doesn't help, can you share more about the arguments you are using to help me debug the issue. I'll try to find time to add documentation for FastHerbie() in the next week or so.

[blaylockbk]

I'm closing this for now since I think the FastHerbie class addresses this (and is better documented). If you continue to have issues, please feel free to reopon.