reki 2025.7.2

A data preparation tool for CEMC/CMA.

reki

A data preparation tool for meteorological data in CEMC/CMA.

Load GRIB2 data using eccodes or cfgrib.

中文文档 (Chinese documentation): https://reki.readthedocs.io/

Installation

Install from pip:

pip install reki

or download the latest source code from GitHub and install using pip.

reki uses ecCodes to decode GRIB files (which is needed by eccodes and cfgrib). Please install ecCodes through conda or other package source.

Getting started

reki has several functions to help users to find one filed from a local GRIB 2 file.

load_message_from_file from reki.format.grib.eccodes returns a GRIB handler. Users can use it to get attrs or values with functions from eccodes .

For example, load 850hPa temperature from CMA-GFS and get values from the returned message.

>>> from reki.format.grib.eccodes import load_message_from_file
>>> t = load_message_from_file(
...     file_path="/g3/COMMONDATA/OPER/CEMC/GFS_GMF/Prod-grib/2024040800/ORIG/gmf.gra.2024040800024.grb2",
...     parameter="t",
...     level_type="isobaricInhPa",
...     level=850,
... )
>>> data = eccodes.codes_get_double_array(t, "values")
>>> data = data.reshape([1440, 2880])
>>> data
array([[252.51597656, 252.51597656, 252.51597656, ..., 252.51597656,
        252.51597656, 252.50597656],
       [252.45597656, 252.45597656, 252.45597656, ..., 252.45597656,
        252.45597656, 252.45597656],
       [252.35597656, 252.35597656, 252.36597656, ..., 252.35597656,
        252.35597656, 252.35597656],
       ...,
       [234.68597656, 234.77597656, 234.77597656, ..., 234.19597656,
        234.28597656, 234.45597656],
       [234.20597656, 234.28597656, 234.61597656, ..., 234.55597656,
        234.40597656, 234.28597656],
       [234.24597656, 234.26597656, 234.28597656, ..., 234.26597656,
        234.25597656, 234.24597656]])

NOTE: Please release the handler using eccodes.codes_release manually.

eccodes engine also provides some functions to load array from GRIB2 file in which GRIB2 message is loaded by eccodes-python and converted into xarray.DataArray by reki.

>>> from reki.format.grib.eccodes import load_field_from_file
>>> load_field_from_file(
...     file_path="/g3/COMMONDATA/OPER/CEMC/GFS_GMF/Prod-grib/2024040800/ORIG/gmf.gra.2024040800024.grb2",
...     parameter="t",
...     level_type="pl",
...     level=850,
... )
<xarray.DataArray 't' (latitude: 1440, longitude: 2880)> Size: 33MB
array([[252.51597656, 252.51597656, 252.51597656, ..., 252.51597656,
        252.51597656, 252.50597656],
       [252.45597656, 252.45597656, 252.45597656, ..., 252.45597656,
        252.45597656, 252.45597656],
       [252.35597656, 252.35597656, 252.36597656, ..., 252.35597656,
        252.35597656, 252.35597656],
       ...,
       [234.68597656, 234.77597656, 234.77597656, ..., 234.19597656,
        234.28597656, 234.45597656],
       [234.20597656, 234.28597656, 234.61597656, ..., 234.55597656,
        234.40597656, 234.28597656],
       [234.24597656, 234.26597656, 234.28597656, ..., 234.26597656,
        234.25597656, 234.24597656]])
Coordinates:
    time        datetime64[ns] 8B 2024-04-08
    step        timedelta64[ns] 8B 1 days
    valid_time  datetime64[ns] 8B 2024-04-09
    pl          float64 8B 850.0
  * latitude    (latitude) float64 12kB 89.94 89.81 89.69 ... -89.81 -89.94
  * longitude   (longitude) float64 23kB 0.0 0.125 0.25 ... 359.6 359.8 359.9
Attributes: (12/17)
    GRIB_edition:             2
    GRIB_centre:              babj
    GRIB_subCentre:           0
    GRIB_tablesVersion:       4
    GRIB_localTablesVersion:  0
    GRIB_dataType:            fc
    ...                       ...
    GRIB_stepType:            instant
    GRIB_stepUnits:           1
    GRIB_stepRange:           24
    GRIB_endStep:             24
    GRIB_count:               109
    long_name:                discipline=0 parmcat=0 parm=0

If the field doesn't have a shortName, use dict for parameter.

Load a filed without shortName.

>>> load_field_from_file(
...     file_path="/g3/COMMONDATA/OPER/CEMC/GFS_GMF/Prod-grib/2024040800/ORIG/gmf.gra.2024040800024.grb2",
...     parameter={
...         "discipline": 0,
...         "parameterCategory": 2,
...         "parameterNumber": 225,
...     },
...     level_type="isobaricInhPa",
...     level=850,
... )
<xarray.DataArray '0_2_225' (latitude: 1440, longitude: 2880)> Size: 33MB
array([[ 1.96391602e-11,  1.96391602e-11, -1.03608398e-11, ...,
        -4.43608398e-11, -6.73608398e-11, -6.73608398e-11],
       [ 1.36391602e-11,  1.36391602e-11, -8.36083984e-12, ...,
        -3.03608398e-11, -3.83608398e-11, -3.83608398e-11],
       [ 1.66391602e-11,  1.66391602e-11,  1.46391602e-11, ...,
         9.63916016e-12,  1.56391602e-11,  1.56391602e-11],
       ...,
       [ 3.06391602e-11,  3.06391602e-11,  4.06391602e-11, ...,
        -4.36083984e-12, -3.53608398e-11, -3.53608398e-11],
       [ 6.56391602e-11,  6.56391602e-11,  6.26391602e-11, ...,
        -2.23608398e-11,  2.63916016e-12,  2.63916016e-12],
       [ 6.56391602e-11,  6.56391602e-11,  6.16391602e-11, ...,
        -2.23608398e-11,  2.63916016e-12,  2.63916016e-12]])
Coordinates:
    time           datetime64[ns] 8B 2024-04-08
    step           timedelta64[ns] 8B 1 days
    valid_time     datetime64[ns] 8B 2024-04-09
    isobaricInhPa  int64 8B 850
  * latitude       (latitude) float64 12kB 89.94 89.81 89.69 ... -89.81 -89.94
  * longitude      (longitude) float64 23kB 0.0 0.125 0.25 ... 359.6 359.8 359.9
Attributes: (12/17)
    GRIB_edition:             2
    GRIB_centre:              babj
    GRIB_subCentre:           0
    GRIB_tablesVersion:       4
    GRIB_localTablesVersion:  1
    GRIB_dataType:            fc
    ...                       ...
    GRIB_stepType:            instant
    GRIB_stepUnits:           1
    GRIB_stepRange:           24
    GRIB_endStep:             24
    GRIB_count:               826
    long_name:                discipline=0 parmcat=2 parm=225

Engines

reki loads GRIB2 file using eccodes by default and also supports cfgrib.

cfgrib

If you don't care about loading speed, please use cfgrib engine with option engine="cfgrib".

Please install cfgrib before using this engine.

Read 850hPa temperature from a CMA-GFS grib2 file using shortName key t. ( shortName is an ecCodes key. )

>>> from reki.format.grib import load_field_from_file
>>> load_field_from_file(
...     file_path="/g3/COMMONDATA/OPER/CEMC/GFS_GMF/Prod-grib/2024040800/ORIG/gmf.gra.2024040800024.grb2",
...     parameter="t",
...     level_type="isobaricInhPa",
...     level=850,
...     engine="cfgrib",
... )
<xarray.DataArray 't' (latitude: 1440, longitude: 2880)> Size: 17MB
[4147200 values with dtype=float32]
Coordinates:
    time           datetime64[ns] 8B ...
    step           timedelta64[ns] 8B ...
    isobaricInhPa  float64 8B ...
  * latitude       (latitude) float64 12kB 89.94 89.81 89.69 ... -89.81 -89.94
  * longitude      (longitude) float64 23kB 0.0 0.125 0.25 ... 359.6 359.8 359.9
    valid_time     datetime64[ns] 8B ...
Attributes: (12/32)
    GRIB_paramId:                             130
    GRIB_dataType:                            fc
    GRIB_numberOfPoints:                      4147200
    GRIB_typeOfLevel:                         isobaricInhPa
    GRIB_stepUnits:                           1
    GRIB_stepType:                            instant
    ...                                       ...
    GRIB_parameterNumber:                     0
    GRIB_shortName:                           t
    GRIB_units:                               K
    long_name:                                Temperature
    units:                                    K
    standard_name:                            air_temperature

Examples

See cemc-oper/data-notebook project for more examples.

LICENSE

Copyright © 2020-2025, developers at cemc-oper.

reki is licensed under Apache License, Version 2.0