diff --git a/README.md b/README.md
index 232888d..27acaeb 100644
--- a/README.md
+++ b/README.md
@@ -15,29 +15,29 @@ naming conventions you can:
 
 >>> import xarray as xr
 >>> import cf2cdm
->>> ds = xr.open_dataset('tests/sample-data/era5-levels-members.grib', engine='cfgrib')
+>>> ds = xr.open_dataset('tests/sample-data/era5-levels-members.zarr')
 >>> cf2cdm.translate_coords(ds, cf2cdm.ECMWF)
 <xarray.Dataset>
-Dimensions:     (time: 4, number: 10, level: 2, latitude: 61, longitude: 120)
+Dimensions:     (number: 10, time: 4, level: 2, latitude: 61, longitude: 120)
 Coordinates:
-  * time        (time) datetime64[ns] 2017-01-01 ... 2017-01-02T12:00:00
     step        timedelta64[ns] ...
+  * time        (time) datetime64[ns] 2017-01-01 ... 2017-01-02T12:00:00
     valid_time  (time) datetime64[ns] ...
   * 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
   * level       (level) float64 850.0 500.0
   * number      (number) int64 0 1 2 3 4 5 6 7 8 9
 Data variables:
-    z           (number, time, level, latitude, longitude) float32 ...
     t           (number, time, level, latitude, longitude) float32 ...
+    z           (number, time, level, latitude, longitude) float32 ...
 Attributes:
-    GRIB_edition:            1
+    Conventions:             CF-1.7
     GRIB_centre:             ecmf
     GRIB_centreDescription:  European Centre for Medium-Range Weather Forecasts
+    GRIB_edition:            1
     GRIB_subCentre:          0
-    Conventions:             CF-1.7
-    institution:             European Centre for Medium-Range Weather Forecasts
     history:                 ...
+    institution:             European Centre for Medium-Range Weather Forecasts
 
 ```
 
@@ -48,27 +48,27 @@ To translate to the Common Data Model of the Climate Data Store use:
 >>> import cf2cdm
 >>> cf2cdm.translate_coords(ds, cf2cdm.CDS)
 <xarray.Dataset>
-Dimensions:                  (forecast_reference_time: 4, realization: 10,
+Dimensions:                  (realization: 10, forecast_reference_time: 4,
                               plev: 2, lat: 61, lon: 120)
 Coordinates:
-  * forecast_reference_time  (forecast_reference_time) datetime64[ns] 2017-01...
     leadtime                 timedelta64[ns] ...
+  * forecast_reference_time  (forecast_reference_time) datetime64[ns] 2017-01...
     time                     (forecast_reference_time) datetime64[ns] ...
   * lat                      (lat) float64 -90.0 -87.0 -84.0 ... 84.0 87.0 90.0
   * lon                      (lon) float64 0.0 3.0 6.0 9.0 ... 351.0 354.0 357.0
   * plev                     (plev) float64 8.5e+04 5e+04
   * realization              (realization) int64 0 1 2 3 4 5 6 7 8 9
 Data variables:
-    z                        (realization, forecast_reference_time, plev, lat, lon) float32 ...
     t                        (realization, forecast_reference_time, plev, lat, lon) float32 ...
+    z                        (realization, forecast_reference_time, plev, lat, lon) float32 ...
 Attributes:
-    GRIB_edition:            1
+    Conventions:             CF-1.7
     GRIB_centre:             ecmf
     GRIB_centreDescription:  European Centre for Medium-Range Weather Forecasts
+    GRIB_edition:            1
     GRIB_subCentre:          0
-    Conventions:             CF-1.7
-    institution:             European Centre for Medium-Range Weather Forecasts
     history:                 ...
+    institution:             European Centre for Medium-Range Weather Forecasts
 
 ```
 
diff --git a/ci/environment-ci.yml b/ci/environment-ci.yml
index 12f6016..3c23072 100644
--- a/ci/environment-ci.yml
+++ b/ci/environment-ci.yml
@@ -15,4 +15,4 @@ dependencies:
 - pip:
   - sphinx-autoapi
 # DO NOT EDIT ABOVE THIS LINE, ADD DEPENDENCIES BELOW
-- cfgrib
+- zarr
diff --git a/tests/sample-data/era5-levels-members.grib b/tests/sample-data/era5-levels-members.grib
deleted file mode 100644
index 9ad18de..0000000
Binary files a/tests/sample-data/era5-levels-members.grib and /dev/null differ
diff --git a/tests/sample-data/era5-levels-members.zarr/.zattrs b/tests/sample-data/era5-levels-members.zarr/.zattrs
new file mode 100644
index 0000000..b6ffc42
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/.zattrs
@@ -0,0 +1,9 @@
+{
+    "Conventions": "CF-1.7",
+    "GRIB_centre": "ecmf",
+    "GRIB_centreDescription": "European Centre for Medium-Range Weather Forecasts",
+    "GRIB_edition": 1,
+    "GRIB_subCentre": 0,
+    "history": "2023-10-15T20:41 GRIB to CDM+CF via cfgrib-0.9.10.4/ecCodes-2.32.0 with {\"source\": \"tests/sample-data/era5-levels-members.grib\", \"filter_by_keys\": {}, \"encode_cf\": [\"parameter\", \"time\", \"geography\", \"vertical\"]}",
+    "institution": "European Centre for Medium-Range Weather Forecasts"
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/.zgroup b/tests/sample-data/era5-levels-members.zarr/.zgroup
new file mode 100644
index 0000000..3b7daf2
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/.zgroup
@@ -0,0 +1,3 @@
+{
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/.zmetadata b/tests/sample-data/era5-levels-members.zarr/.zmetadata
new file mode 100644
index 0000000..a2f93b8
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/.zmetadata
@@ -0,0 +1,342 @@
+{
+    "metadata": {
+        ".zattrs": {
+            "Conventions": "CF-1.7",
+            "GRIB_centre": "ecmf",
+            "GRIB_centreDescription": "European Centre for Medium-Range Weather Forecasts",
+            "GRIB_edition": 1,
+            "GRIB_subCentre": 0,
+            "history": "2023-10-15T20:41 GRIB to CDM+CF via cfgrib-0.9.10.4/ecCodes-2.32.0 with {\"source\": \"tests/sample-data/era5-levels-members.grib\", \"filter_by_keys\": {}, \"encode_cf\": [\"parameter\", \"time\", \"geography\", \"vertical\"]}",
+            "institution": "European Centre for Medium-Range Weather Forecasts"
+        },
+        ".zgroup": {
+            "zarr_format": 2
+        },
+        "isobaricInhPa/.zarray": {
+            "chunks": [
+                2
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                2
+            ],
+            "zarr_format": 2
+        },
+        "isobaricInhPa/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "isobaricInhPa"
+            ],
+            "long_name": "pressure",
+            "positive": "down",
+            "standard_name": "air_pressure",
+            "stored_direction": "decreasing",
+            "units": "hPa"
+        },
+        "latitude/.zarray": {
+            "chunks": [
+                61
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                61
+            ],
+            "zarr_format": 2
+        },
+        "latitude/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "latitude"
+            ],
+            "long_name": "latitude",
+            "standard_name": "latitude",
+            "stored_direction": "decreasing",
+            "units": "degrees_north"
+        },
+        "longitude/.zarray": {
+            "chunks": [
+                120
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                120
+            ],
+            "zarr_format": 2
+        },
+        "longitude/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "longitude"
+            ],
+            "long_name": "longitude",
+            "standard_name": "longitude",
+            "units": "degrees_east"
+        },
+        "number/.zarray": {
+            "chunks": [
+                10
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<i8",
+            "fill_value": null,
+            "filters": null,
+            "order": "C",
+            "shape": [
+                10
+            ],
+            "zarr_format": 2
+        },
+        "number/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "number"
+            ],
+            "long_name": "ensemble member numerical id",
+            "standard_name": "realization",
+            "units": "1"
+        },
+        "step/.zarray": {
+            "chunks": [],
+            "compressor": null,
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [],
+            "zarr_format": 2
+        },
+        "step/.zattrs": {
+            "_ARRAY_DIMENSIONS": [],
+            "long_name": "time since forecast_reference_time",
+            "standard_name": "forecast_period",
+            "units": "hours"
+        },
+        "t/.zarray": {
+            "chunks": [
+                10,
+                4,
+                2,
+                61,
+                120
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f4",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                10,
+                4,
+                2,
+                61,
+                120
+            ],
+            "zarr_format": 2
+        },
+        "t/.zattrs": {
+            "GRIB_NV": 0,
+            "GRIB_Nx": 120,
+            "GRIB_Ny": 61,
+            "GRIB_cfName": "air_temperature",
+            "GRIB_cfVarName": "t",
+            "GRIB_dataType": "an",
+            "GRIB_gridDefinitionDescription": "Latitude/Longitude Grid",
+            "GRIB_gridType": "regular_ll",
+            "GRIB_iDirectionIncrementInDegrees": 3.0,
+            "GRIB_iScansNegatively": 0,
+            "GRIB_jDirectionIncrementInDegrees": 3.0,
+            "GRIB_jPointsAreConsecutive": 0,
+            "GRIB_jScansPositively": 0,
+            "GRIB_latitudeOfFirstGridPointInDegrees": 90.0,
+            "GRIB_latitudeOfLastGridPointInDegrees": -90.0,
+            "GRIB_longitudeOfFirstGridPointInDegrees": 0.0,
+            "GRIB_longitudeOfLastGridPointInDegrees": 357.0,
+            "GRIB_missingValue": 3.4028234663852886e+38,
+            "GRIB_name": "Temperature",
+            "GRIB_numberOfPoints": 7320,
+            "GRIB_paramId": 130,
+            "GRIB_shortName": "t",
+            "GRIB_stepType": "instant",
+            "GRIB_stepUnits": 1,
+            "GRIB_totalNumber": 10,
+            "GRIB_typeOfLevel": "isobaricInhPa",
+            "GRIB_units": "K",
+            "_ARRAY_DIMENSIONS": [
+                "number",
+                "time",
+                "isobaricInhPa",
+                "latitude",
+                "longitude"
+            ],
+            "coordinates": "number time step isobaricInhPa latitude longitude valid_time",
+            "long_name": "Temperature",
+            "standard_name": "air_temperature",
+            "units": "K"
+        },
+        "time/.zarray": {
+            "chunks": [
+                4
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<i8",
+            "fill_value": null,
+            "filters": null,
+            "order": "C",
+            "shape": [
+                4
+            ],
+            "zarr_format": 2
+        },
+        "time/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "time"
+            ],
+            "calendar": "proleptic_gregorian",
+            "long_name": "initial time of forecast",
+            "standard_name": "forecast_reference_time",
+            "units": "seconds since 1970-01-01"
+        },
+        "valid_time/.zarray": {
+            "chunks": [
+                4
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                4
+            ],
+            "zarr_format": 2
+        },
+        "valid_time/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "time"
+            ],
+            "calendar": "proleptic_gregorian",
+            "long_name": "time",
+            "standard_name": "time",
+            "units": "seconds since 1970-01-01"
+        },
+        "z/.zarray": {
+            "chunks": [
+                10,
+                4,
+                2,
+                61,
+                120
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
+                "shuffle": 1
+            },
+            "dtype": "<f4",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [
+                10,
+                4,
+                2,
+                61,
+                120
+            ],
+            "zarr_format": 2
+        },
+        "z/.zattrs": {
+            "GRIB_NV": 0,
+            "GRIB_Nx": 120,
+            "GRIB_Ny": 61,
+            "GRIB_cfName": "geopotential",
+            "GRIB_cfVarName": "z",
+            "GRIB_dataType": "an",
+            "GRIB_gridDefinitionDescription": "Latitude/Longitude Grid",
+            "GRIB_gridType": "regular_ll",
+            "GRIB_iDirectionIncrementInDegrees": 3.0,
+            "GRIB_iScansNegatively": 0,
+            "GRIB_jDirectionIncrementInDegrees": 3.0,
+            "GRIB_jPointsAreConsecutive": 0,
+            "GRIB_jScansPositively": 0,
+            "GRIB_latitudeOfFirstGridPointInDegrees": 90.0,
+            "GRIB_latitudeOfLastGridPointInDegrees": -90.0,
+            "GRIB_longitudeOfFirstGridPointInDegrees": 0.0,
+            "GRIB_longitudeOfLastGridPointInDegrees": 357.0,
+            "GRIB_missingValue": 3.4028234663852886e+38,
+            "GRIB_name": "Geopotential",
+            "GRIB_numberOfPoints": 7320,
+            "GRIB_paramId": 129,
+            "GRIB_shortName": "z",
+            "GRIB_stepType": "instant",
+            "GRIB_stepUnits": 1,
+            "GRIB_totalNumber": 10,
+            "GRIB_typeOfLevel": "isobaricInhPa",
+            "GRIB_units": "m**2 s**-2",
+            "_ARRAY_DIMENSIONS": [
+                "number",
+                "time",
+                "isobaricInhPa",
+                "latitude",
+                "longitude"
+            ],
+            "coordinates": "number time step isobaricInhPa latitude longitude valid_time",
+            "long_name": "Geopotential",
+            "standard_name": "geopotential",
+            "units": "m**2 s**-2"
+        }
+    },
+    "zarr_consolidated_format": 1
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zarray b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zarray
new file mode 100644
index 0000000..63549b5
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zarray
@@ -0,0 +1,20 @@
+{
+    "chunks": [
+        2
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [
+        2
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zattrs b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zattrs
new file mode 100644
index 0000000..0e5cb0f
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/.zattrs
@@ -0,0 +1,10 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "isobaricInhPa"
+    ],
+    "long_name": "pressure",
+    "positive": "down",
+    "standard_name": "air_pressure",
+    "stored_direction": "decreasing",
+    "units": "hPa"
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/0 b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/0
new file mode 100644
index 0000000..69ef1c6
Binary files /dev/null and b/tests/sample-data/era5-levels-members.zarr/isobaricInhPa/0 differ
diff --git a/tests/sample-data/era5-levels-members.zarr/latitude/.zarray b/tests/sample-data/era5-levels-members.zarr/latitude/.zarray
new file mode 100644
index 0000000..57a7696
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/latitude/.zarray
@@ -0,0 +1,20 @@
+{
+    "chunks": [
+        61
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [
+        61
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/latitude/.zattrs b/tests/sample-data/era5-levels-members.zarr/latitude/.zattrs
new file mode 100644
index 0000000..04311f1
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/latitude/.zattrs
@@ -0,0 +1,9 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "latitude"
+    ],
+    "long_name": "latitude",
+    "standard_name": "latitude",
+    "stored_direction": "decreasing",
+    "units": "degrees_north"
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/latitude/0 b/tests/sample-data/era5-levels-members.zarr/latitude/0
new file mode 100644
index 0000000..fa6ab1e
Binary files /dev/null and b/tests/sample-data/era5-levels-members.zarr/latitude/0 differ
diff --git a/tests/sample-data/era5-levels-members.zarr/longitude/.zarray b/tests/sample-data/era5-levels-members.zarr/longitude/.zarray
new file mode 100644
index 0000000..d044b1c
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/longitude/.zarray
@@ -0,0 +1,20 @@
+{
+    "chunks": [
+        120
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [
+        120
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/longitude/.zattrs b/tests/sample-data/era5-levels-members.zarr/longitude/.zattrs
new file mode 100644
index 0000000..a53d852
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/longitude/.zattrs
@@ -0,0 +1,8 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "longitude"
+    ],
+    "long_name": "longitude",
+    "standard_name": "longitude",
+    "units": "degrees_east"
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/longitude/0 b/tests/sample-data/era5-levels-members.zarr/longitude/0
new file mode 100644
index 0000000..5675e44
Binary files /dev/null and b/tests/sample-data/era5-levels-members.zarr/longitude/0 differ
diff --git a/tests/sample-data/era5-levels-members.zarr/number/.zarray b/tests/sample-data/era5-levels-members.zarr/number/.zarray
new file mode 100644
index 0000000..f24b055
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/number/.zarray
@@ -0,0 +1,20 @@
+{
+    "chunks": [
+        10
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<i8",
+    "fill_value": null,
+    "filters": null,
+    "order": "C",
+    "shape": [
+        10
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/number/.zattrs b/tests/sample-data/era5-levels-members.zarr/number/.zattrs
new file mode 100644
index 0000000..0f5cf2c
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/number/.zattrs
@@ -0,0 +1,8 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "number"
+    ],
+    "long_name": "ensemble member numerical id",
+    "standard_name": "realization",
+    "units": "1"
+}
\ No newline at end of file
diff --git a/tests/sample-data/era5-levels-members.zarr/number/0 b/tests/sample-data/era5-levels-members.zarr/number/0
new file mode 100644
index 0000000..db12d08
Binary files /dev/null and b/tests/sample-data/era5-levels-members.zarr/number/0 differ
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new file mode 100644
index 0000000..d04b282
--- /dev/null
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+    "compressor": null,
+    "dtype": "<f8",
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new file mode 100644
index 0000000..dccb35a
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/step/.zattrs
@@ -0,0 +1,6 @@
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+    "long_name": "time since forecast_reference_time",
+    "standard_name": "forecast_period",
+    "units": "hours"
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\ No newline at end of file
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new file mode 100644
index 0000000..3664b68
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+    "filters": null,
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new file mode 100644
index 0000000..bb3e5ca
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/t/.zattrs
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+    "GRIB_Nx": 120,
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+    "GRIB_cfVarName": "t",
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+    "GRIB_longitudeOfLastGridPointInDegrees": 357.0,
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+    "GRIB_numberOfPoints": 7320,
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+    "GRIB_totalNumber": 10,
+    "GRIB_typeOfLevel": "isobaricInhPa",
+    "GRIB_units": "K",
+    "_ARRAY_DIMENSIONS": [
+        "number",
+        "time",
+        "isobaricInhPa",
+        "latitude",
+        "longitude"
+    ],
+    "coordinates": "number time step isobaricInhPa latitude longitude valid_time",
+    "long_name": "Temperature",
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+    "units": "K"
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\ No newline at end of file
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new file mode 100644
index 0000000..36e027a
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/time/.zarray
@@ -0,0 +1,20 @@
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new file mode 100644
index 0000000..c7317ff
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/time/.zattrs
@@ -0,0 +1,9 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "time"
+    ],
+    "calendar": "proleptic_gregorian",
+    "long_name": "initial time of forecast",
+    "standard_name": "forecast_reference_time",
+    "units": "seconds since 1970-01-01"
+}
\ No newline at end of file
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new file mode 100644
index 0000000..eb6c239
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+++ b/tests/sample-data/era5-levels-members.zarr/valid_time/.zarray
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new file mode 100644
index 0000000..bc53309
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/valid_time/.zattrs
@@ -0,0 +1,9 @@
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+    "long_name": "time",
+    "standard_name": "time",
+    "units": "seconds since 1970-01-01"
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Binary files /dev/null and b/tests/sample-data/era5-levels-members.zarr/valid_time/0 differ
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new file mode 100644
index 0000000..3664b68
--- /dev/null
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+        4,
+        2,
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new file mode 100644
index 0000000..02daf88
--- /dev/null
+++ b/tests/sample-data/era5-levels-members.zarr/z/.zattrs
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+    "GRIB_Nx": 120,
+    "GRIB_Ny": 61,
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+    "GRIB_cfVarName": "z",
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+    "GRIB_longitudeOfLastGridPointInDegrees": 357.0,
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+        "number",
+        "time",
+        "isobaricInhPa",
+        "latitude",
+        "longitude"
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+    "long_name": "Geopotential",
+    "standard_name": "geopotential",
+    "units": "m**2 s**-2"
+}
\ No newline at end of file
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deleted file mode 100644
index 186143a..0000000
Binary files a/tests/sample-data/lambert_grid.grib and /dev/null differ
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new file mode 100644
index 0000000..1fecfc1
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/.zattrs
@@ -0,0 +1,9 @@
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+    "Conventions": "CF-1.7",
+    "GRIB_centre": "96",
+    "GRIB_centreDescription": "Athens",
+    "GRIB_edition": 1,
+    "GRIB_subCentre": 99,
+    "history": "2023-10-15T20:40 GRIB to CDM+CF via cfgrib-0.9.10.4/ecCodes-2.32.0 with {\"source\": \"tests/sample-data/lambert_grid.grib\", \"filter_by_keys\": {}, \"encode_cf\": [\"parameter\", \"time\", \"geography\", \"vertical\"]}",
+    "institution": "Athens"
+}
\ No newline at end of file
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new file mode 100644
index 0000000..3b7daf2
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/.zgroup
@@ -0,0 +1,3 @@
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+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/.zmetadata b/tests/sample-data/lambert_grid.zarr/.zmetadata
new file mode 100644
index 0000000..9fdad12
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/.zmetadata
@@ -0,0 +1,207 @@
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+    "metadata": {
+        ".zattrs": {
+            "Conventions": "CF-1.7",
+            "GRIB_centre": "96",
+            "GRIB_centreDescription": "Athens",
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+            "GRIB_subCentre": 99,
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+        },
+        ".zgroup": {
+            "zarr_format": 2
+        },
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+            "compressor": null,
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [],
+            "zarr_format": 2
+        },
+        "heightAboveGround/.zattrs": {
+            "_ARRAY_DIMENSIONS": [],
+            "long_name": "height above the surface",
+            "positive": "up",
+            "standard_name": "height",
+            "units": "m"
+        },
+        "latitude/.zarray": {
+            "chunks": [
+                475,
+                475
+            ],
+            "compressor": {
+                "blocksize": 0,
+                "clevel": 5,
+                "cname": "lz4",
+                "id": "blosc",
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+            "order": "C",
+            "shape": [
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+                475
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+            "zarr_format": 2
+        },
+        "latitude/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "y",
+                "x"
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+            "standard_name": "latitude",
+            "units": "degrees_north"
+        },
+        "longitude/.zarray": {
+            "chunks": [
+                475,
+                475
+            ],
+            "compressor": {
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+                "clevel": 5,
+                "cname": "lz4",
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+            "order": "C",
+            "shape": [
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+                475
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+            "zarr_format": 2
+        },
+        "longitude/.zattrs": {
+            "_ARRAY_DIMENSIONS": [
+                "y",
+                "x"
+            ],
+            "long_name": "longitude",
+            "standard_name": "longitude",
+            "units": "degrees_east"
+        },
+        "p3112/.zarray": {
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+                475
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+                "clevel": 5,
+                "cname": "lz4",
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+            "order": "C",
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+            "GRIB_units": "W m**-2",
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+                "y",
+                "x"
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+            "units": "W m**-2"
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+            "compressor": null,
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+            "filters": null,
+            "order": "C",
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+            "zarr_format": 2
+        },
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+        },
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+            "compressor": null,
+            "dtype": "<i8",
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+            "order": "C",
+            "shape": [],
+            "zarr_format": 2
+        },
+        "time/.zattrs": {
+            "_ARRAY_DIMENSIONS": [],
+            "calendar": "proleptic_gregorian",
+            "long_name": "initial time of forecast",
+            "standard_name": "forecast_reference_time",
+            "units": "seconds since 1970-01-01"
+        },
+        "valid_time/.zarray": {
+            "chunks": [],
+            "compressor": null,
+            "dtype": "<f8",
+            "fill_value": "NaN",
+            "filters": null,
+            "order": "C",
+            "shape": [],
+            "zarr_format": 2
+        },
+        "valid_time/.zattrs": {
+            "_ARRAY_DIMENSIONS": [],
+            "calendar": "proleptic_gregorian",
+            "long_name": "time",
+            "standard_name": "time",
+            "units": "seconds since 1970-01-01"
+        }
+    },
+    "zarr_consolidated_format": 1
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zarray b/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zarray
new file mode 100644
index 0000000..d04b282
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zarray
@@ -0,0 +1,10 @@
+{
+    "chunks": [],
+    "compressor": null,
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zattrs b/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zattrs
new file mode 100644
index 0000000..439f0e1
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/heightAboveGround/.zattrs
@@ -0,0 +1,7 @@
+{
+    "_ARRAY_DIMENSIONS": [],
+    "long_name": "height above the surface",
+    "positive": "up",
+    "standard_name": "height",
+    "units": "m"
+}
\ No newline at end of file
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new file mode 100644
index 0000000..1b1cb4d
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/heightAboveGround/0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/latitude/.zarray b/tests/sample-data/lambert_grid.zarr/latitude/.zarray
new file mode 100644
index 0000000..c055a0b
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/latitude/.zarray
@@ -0,0 +1,22 @@
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+        "clevel": 5,
+        "cname": "lz4",
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+    "filters": null,
+    "order": "C",
+    "shape": [
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+}
\ No newline at end of file
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new file mode 100644
index 0000000..a78b0c4
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/latitude/.zattrs
@@ -0,0 +1,9 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "y",
+        "x"
+    ],
+    "long_name": "latitude",
+    "standard_name": "latitude",
+    "units": "degrees_north"
+}
\ No newline at end of file
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new file mode 100644
index 0000000..4e53566
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/latitude/0.0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/longitude/.zarray b/tests/sample-data/lambert_grid.zarr/longitude/.zarray
new file mode 100644
index 0000000..c055a0b
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/longitude/.zarray
@@ -0,0 +1,22 @@
+{
+    "chunks": [
+        475,
+        475
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [
+        475,
+        475
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/longitude/.zattrs b/tests/sample-data/lambert_grid.zarr/longitude/.zattrs
new file mode 100644
index 0000000..b75232b
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/longitude/.zattrs
@@ -0,0 +1,9 @@
+{
+    "_ARRAY_DIMENSIONS": [
+        "y",
+        "x"
+    ],
+    "long_name": "longitude",
+    "standard_name": "longitude",
+    "units": "degrees_east"
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/longitude/0.0 b/tests/sample-data/lambert_grid.zarr/longitude/0.0
new file mode 100644
index 0000000..8df0d7e
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/longitude/0.0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/p3112/.zarray b/tests/sample-data/lambert_grid.zarr/p3112/.zarray
new file mode 100644
index 0000000..f4e1080
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/p3112/.zarray
@@ -0,0 +1,22 @@
+{
+    "chunks": [
+        475,
+        475
+    ],
+    "compressor": {
+        "blocksize": 0,
+        "clevel": 5,
+        "cname": "lz4",
+        "id": "blosc",
+        "shuffle": 1
+    },
+    "dtype": "<f4",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [
+        475,
+        475
+    ],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/p3112/.zattrs b/tests/sample-data/lambert_grid.zarr/p3112/.zattrs
new file mode 100644
index 0000000..0562c4c
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/p3112/.zattrs
@@ -0,0 +1,39 @@
+{
+    "GRIB_DxInMetres": 2500,
+    "GRIB_DyInMetres": 2500,
+    "GRIB_LaDInDegrees": 54,
+    "GRIB_Latin1InDegrees": 54.0,
+    "GRIB_Latin2InDegrees": 54.0,
+    "GRIB_LoVInDegrees": 3.0,
+    "GRIB_NV": 82,
+    "GRIB_Nx": 475,
+    "GRIB_Ny": 475,
+    "GRIB_cfName": "unknown",
+    "GRIB_cfVarName": "p3112",
+    "GRIB_gridDefinitionDescription": "Lambert Conformal",
+    "GRIB_gridType": "lambert",
+    "GRIB_iScansNegatively": 0,
+    "GRIB_jPointsAreConsecutive": 0,
+    "GRIB_jScansPositively": 1,
+    "GRIB_latitudeOfFirstGridPointInDegrees": 48.379,
+    "GRIB_latitudeOfSouthernPoleInDegrees": 0.0,
+    "GRIB_longitudeOfFirstGridPointInDegrees": -5.002,
+    "GRIB_longitudeOfSouthernPoleInDegrees": 0.0,
+    "GRIB_missingValue": 3.4028234663852886e+38,
+    "GRIB_name": "Net long-wave radiation flux (surface)",
+    "GRIB_numberOfPoints": 225625,
+    "GRIB_paramId": 3112,
+    "GRIB_shortName": "nlwrs",
+    "GRIB_stepType": "instant",
+    "GRIB_stepUnits": 1,
+    "GRIB_typeOfLevel": "heightAboveGround",
+    "GRIB_units": "W m**-2",
+    "_ARRAY_DIMENSIONS": [
+        "y",
+        "x"
+    ],
+    "coordinates": "time step heightAboveGround latitude longitude valid_time",
+    "long_name": "Net long-wave radiation flux (surface)",
+    "standard_name": "unknown",
+    "units": "W m**-2"
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/p3112/0.0 b/tests/sample-data/lambert_grid.zarr/p3112/0.0
new file mode 100644
index 0000000..06d068d
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/p3112/0.0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/step/.zarray b/tests/sample-data/lambert_grid.zarr/step/.zarray
new file mode 100644
index 0000000..d04b282
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/step/.zarray
@@ -0,0 +1,10 @@
+{
+    "chunks": [],
+    "compressor": null,
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/step/.zattrs b/tests/sample-data/lambert_grid.zarr/step/.zattrs
new file mode 100644
index 0000000..dccb35a
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/step/.zattrs
@@ -0,0 +1,6 @@
+{
+    "_ARRAY_DIMENSIONS": [],
+    "long_name": "time since forecast_reference_time",
+    "standard_name": "forecast_period",
+    "units": "hours"
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/step/0 b/tests/sample-data/lambert_grid.zarr/step/0
new file mode 100644
index 0000000..3357e67
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/step/0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/time/.zarray b/tests/sample-data/lambert_grid.zarr/time/.zarray
new file mode 100644
index 0000000..4b4c58a
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/time/.zarray
@@ -0,0 +1,10 @@
+{
+    "chunks": [],
+    "compressor": null,
+    "dtype": "<i8",
+    "fill_value": null,
+    "filters": null,
+    "order": "C",
+    "shape": [],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/time/.zattrs b/tests/sample-data/lambert_grid.zarr/time/.zattrs
new file mode 100644
index 0000000..ff710e2
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/time/.zattrs
@@ -0,0 +1,7 @@
+{
+    "_ARRAY_DIMENSIONS": [],
+    "calendar": "proleptic_gregorian",
+    "long_name": "initial time of forecast",
+    "standard_name": "forecast_reference_time",
+    "units": "seconds since 1970-01-01"
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/time/0 b/tests/sample-data/lambert_grid.zarr/time/0
new file mode 100644
index 0000000..cb73789
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/time/0 differ
diff --git a/tests/sample-data/lambert_grid.zarr/valid_time/.zarray b/tests/sample-data/lambert_grid.zarr/valid_time/.zarray
new file mode 100644
index 0000000..d04b282
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/valid_time/.zarray
@@ -0,0 +1,10 @@
+{
+    "chunks": [],
+    "compressor": null,
+    "dtype": "<f8",
+    "fill_value": "NaN",
+    "filters": null,
+    "order": "C",
+    "shape": [],
+    "zarr_format": 2
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/valid_time/.zattrs b/tests/sample-data/lambert_grid.zarr/valid_time/.zattrs
new file mode 100644
index 0000000..3f35eae
--- /dev/null
+++ b/tests/sample-data/lambert_grid.zarr/valid_time/.zattrs
@@ -0,0 +1,7 @@
+{
+    "_ARRAY_DIMENSIONS": [],
+    "calendar": "proleptic_gregorian",
+    "long_name": "time",
+    "standard_name": "time",
+    "units": "seconds since 1970-01-01"
+}
\ No newline at end of file
diff --git a/tests/sample-data/lambert_grid.zarr/valid_time/0 b/tests/sample-data/lambert_grid.zarr/valid_time/0
new file mode 100644
index 0000000..0a2eb61
Binary files /dev/null and b/tests/sample-data/lambert_grid.zarr/valid_time/0 differ
diff --git a/tests/test_50_datamodels.py b/tests/test_50_datamodels.py
index f075d8d..33c08aa 100644
--- a/tests/test_50_datamodels.py
+++ b/tests/test_50_datamodels.py
@@ -5,8 +5,8 @@
 from cf2cdm import cfcoords, datamodels
 
 SAMPLE_DATA_FOLDER = os.path.join(os.path.dirname(__file__), "sample-data")
-TEST_DATA1 = os.path.join(SAMPLE_DATA_FOLDER, "era5-levels-members.grib")
-TEST_DATA2 = os.path.join(SAMPLE_DATA_FOLDER, "lambert_grid.grib")
+TEST_DATA1 = os.path.join(SAMPLE_DATA_FOLDER, "era5-levels-members.zarr")
+TEST_DATA2 = os.path.join(SAMPLE_DATA_FOLDER, "lambert_grid.zarr")
 
 
 def test_cds() -> None: