UK Met Office - C-band rain radar composite

This notebook describes how to access and use the zarr-version of the UK Met Office C-band rain radar 1 km composite dataset. The dataset provides 5-minute precipitation rates in mm/h at 1 km × 1 km spatial resolution over the United Kingdom, derived from the Met Office radar network. The data uses the OSGB 1936 / British National Grid projection (EPSG:27700). The v0.1.0 zarr version of the dataset covers July 2005 to the end of 2025.

The raw NIMROD data was downloaded from CEDA and converted using mlcast-dataset-metoffice-nimrod and mlcast-dataset-tiff2zarr.

import matplotlib.pyplot as plt
import cartopy.crs as ccrs

import mlcast_datasets

cat = mlcast_datasets.open_catalog()
list(cat.precipitation)

['radklim_hourly',
 'radklim_5_minutes',
 'dmi_10_minutes',
 'it_dpc_sri_5min',
 'uk_metoffice_5min',
 'be_rmi_radclim_mfb_5min']

UK Met Office 5-min radar precipitation

The UK Met Office radar dataset is available in the intake catalog as uk_metoffice_5min.

ds = cat.precipitation.uk_metoffice_5min.to_dask()
ds

<xarray.Dataset> Size: 31TB
Dimensions:        (time: 2055276, y: 2175, x: 1725, missing_times: 100404)
Coordinates:
  * time           (time) datetime64[ns] 16MB 2005-07-05 ... 2025-12-31T23:55:00
  * y              (y) float64 17kB 1.55e+06 1.548e+06 ... -6.235e+05 -6.245e+05
  * x              (x) float64 14kB -4.045e+05 -4.035e+05 ... 1.318e+06 1.32e+06
    lat            (y, x) float64 30MB dask.array<chunksize=(2175, 1725), meta=np.ndarray>
    lon            (y, x) float64 30MB dask.array<chunksize=(2175, 1725), meta=np.ndarray>
  * missing_times  (missing_times) datetime64[ns] 803kB 2005-07-05T06:40:00 ....
Data variables:
    crs            float32 4B ...
    RR             (time, y, x) float32 31TB dask.array<chunksize=(1, 2175, 1725), meta=np.ndarray>
Attributes:
    title:                      UK Met Office C-band rain radar 1 km composite
    license:                    OGL-UK-3.0
    history:                    Created at 2026-02-16T22:33:20+01:00
    mlcast_created_on:          2026-02-16T22:33:20+01:00
    mlcast_created_by:          Gabriele Franch <franch@fbk.eu>
    mlcast_created_with:        https://github.com/mlcast-community/mlcast-da...
    mlcast_dataset_version:     0.1.0
    mlcast_dataset_identifier:  UK-METOFFICE-RADAR
    consistent_timestep_start:  2005-07-05T00:00
    base_frequencies:           5min:2005-07-05T00:00/None

xarray.Dataset

• Dimensions:
  • time: 2055276
  • y: 2175
  • x: 1725
  • missing_times: 100404
• Coordinates: (6)
  • time
    (time)
    datetime64[ns]
    2005-07-05 ... 2025-12-31T23:55:00

    long_name :

    Time

    standard_name :

    time

    array(['2005-07-05T00:00:00.000000000', '2005-07-05T00:05:00.000000000',
           '2005-07-05T00:10:00.000000000', ..., '2025-12-31T23:45:00.000000000',
           '2025-12-31T23:50:00.000000000', '2025-12-31T23:55:00.000000000'],
          shape=(2055276,), dtype='datetime64[ns]')

  • y
    (y)
    float64
    1.55e+06 1.548e+06 ... -6.245e+05

    units :

    m

    array([1549500., 1548500., 1547500., ..., -622500., -623500., -624500.],
          shape=(2175,))

  • x
    (x)
    float64
    -4.045e+05 -4.035e+05 ... 1.32e+06

    units :

    m

    array([-404500., -403500., -402500., ..., 1317500., 1318500., 1319500.],
          shape=(1725,))

  • lat
    (y, x)
    float64
    dask.array<chunksize=(2175, 1725), meta=np.ndarray>

    grid_mapping :

    crs

    long_name :

    Latitude

    standard_name :

    latitude

    units :

    degrees_north

    Array Chunk Bytes 28.62 MiB 28.62 MiB Shape (2175, 1725) (2175, 1725) Dask graph 1 chunks in 2 graph layers Data type float64 numpy.ndarray

  • lon
    (y, x)
    float64
    dask.array<chunksize=(2175, 1725), meta=np.ndarray>

    grid_mapping :

    crs

    long_name :

    Longitude

    standard_name :

    longitude

    units :

    degrees_east

    Array Chunk Bytes 28.62 MiB 28.62 MiB Shape (2175, 1725) (2175, 1725) Dask graph 1 chunks in 2 graph layers Data type float64 numpy.ndarray

  • missing_times
    (missing_times)
    datetime64[ns]
    2005-07-05T06:40:00 ... 2025-12-...

    array(['2005-07-05T06:40:00.000000000', '2005-07-05T18:30:00.000000000',
           '2005-07-07T06:15:00.000000000', ..., '2025-12-19T07:20:00.000000000',
           '2025-12-19T07:25:00.000000000', '2025-12-19T07:30:00.000000000'],
          shape=(100404,), dtype='datetime64[ns]')

• Data variables: (2)
  • crs
    ()
    float32
    ...

    crs_wkt :

    PROJCRS["OSGB36 / British National Grid",BASEGEOGCRS["OSGB36",DATUM["Ordnance Survey of Great Britain 1936",ELLIPSOID["Airy 1830",6377563.396,299.3249646,LENGTHUNIT["metre",1]]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],ID["EPSG",4277]],CONVERSION["unnamed",METHOD["Transverse Mercator",ID["EPSG",9807]],PARAMETER["Latitude of natural origin",49,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8801]],PARAMETER["Longitude of natural origin",-2,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Scale factor at natural origin",0.9996012717,SCALEUNIT["unity",1],ID["EPSG",8805]],PARAMETER["False easting",400000,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",-100000,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["easting",east,ORDER[1],LENGTHUNIT["metre",1]],AXIS["northing",north,ORDER[2],LENGTHUNIT["metre",1]],ID["EPSG",27700],BBOX[43.7059070319628,-17.96210452914792,62.917497425514036,16.117076756169485]]

    spatial_ref :

    PROJCRS["OSGB36 / British National Grid",BASEGEOGCRS["OSGB36",DATUM["Ordnance Survey of Great Britain 1936",ELLIPSOID["Airy 1830",6377563.396,299.3249646,LENGTHUNIT["metre",1]]],PRIMEM["Greenwich",0,ANGLEUNIT["degree",0.0174532925199433]],ID["EPSG",4277]],CONVERSION["unnamed",METHOD["Transverse Mercator",ID["EPSG",9807]],PARAMETER["Latitude of natural origin",49,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8801]],PARAMETER["Longitude of natural origin",-2,ANGLEUNIT["degree",0.0174532925199433],ID["EPSG",8802]],PARAMETER["Scale factor at natural origin",0.9996012717,SCALEUNIT["unity",1],ID["EPSG",8805]],PARAMETER["False easting",400000,LENGTHUNIT["metre",1],ID["EPSG",8806]],PARAMETER["False northing",-100000,LENGTHUNIT["metre",1],ID["EPSG",8807]]],CS[Cartesian,2],AXIS["easting",east,ORDER[1],LENGTHUNIT["metre",1]],AXIS["northing",north,ORDER[2],LENGTHUNIT["metre",1]],ID["EPSG",27700]]

    GeoTransform :

    -405000.0 1000.0 0.0 1550000.0 0.0 -1000.0

    proj4 :

    +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +units=m +no_defs +type=crs

    semi_major_axis :

    6377563.396

    semi_minor_axis :

    6356256.909237285

    inverse_flattening :

    299.3249646

    reference_ellipsoid_name :

    Airy 1830

    longitude_of_prime_meridian :

    0.0

    prime_meridian_name :

    Greenwich

    geographic_crs_name :

    OSGB36

    horizontal_datum_name :

    Ordnance Survey of Great Britain 1936

    projected_crs_name :

    OSGB36 / British National Grid

    grid_mapping_name :

    transverse_mercator

    latitude_of_projection_origin :

    49.0

    longitude_of_central_meridian :

    -2.0

    false_easting :

    400000.0

    false_northing :

    -100000.0

    scale_factor_at_central_meridian :

    0.9996012717

    [1 values with dtype=float32]

  • RR
    (time, y, x)
    float32
    dask.array<chunksize=(1, 2175, 1725), meta=np.ndarray>

    grid_mapping :

    crs

    long_name :

    Radar precipitation rate

    standard_name :

    rainfall_flux

    units :

    kg m-2 h-1

    Array Chunk Bytes 28.05 TiB 14.31 MiB Shape (2055276, 2175, 1725) (1, 2175, 1725) Dask graph 2055276 chunks in 2 graph layers Data type float32 numpy.ndarray

• Attributes: (10)

  title :

  UK Met Office C-band rain radar 1 km composite

  license :

  OGL-UK-3.0

  history :

  Created at 2026-02-16T22:33:20+01:00

  mlcast_created_on :

  2026-02-16T22:33:20+01:00

  mlcast_created_by :

  Gabriele Franch <franch@fbk.eu>

  mlcast_created_with :

  https://github.com/mlcast-community/mlcast-dataset-metoffice-nimrod@v0.1.0

  mlcast_dataset_version :

  0.1.0

  mlcast_dataset_identifier :

  UK-METOFFICE-RADAR

  consistent_timestep_start :

  2005-07-05T00:00

  base_frequencies :

  5min:2005-07-05T00:00/None

var_name = "RR"

crs_name = ds[var_name].grid_mapping
data_crs = ccrs.Projection(ds[crs_name].crs_wkt)

g = (
    ds[var_name]
    .sel(time="2020-10-03T12")
    .isel(time=slice(None, 3))
    .plot(
        transform=data_crs,
        cmap="viridis",
        add_colorbar=True,
        col="time",
        robust=True,
        subplot_kws=dict(projection=data_crs),
        vmin=0,
    )
)

for ax in g.axs.flat:
    ax.coastlines()
    ax.gridlines(draw_labels=["top", "left"])

/home/runner/work/mlcast-datasets/mlcast-datasets/.venv/lib/python3.12/site-packages/cartopy/io/__init__.py:242: DownloadWarning: Downloading: https://naturalearth.s3.amazonaws.com/50m_physical/ne_50m_coastline.zip
  warnings.warn(f'Downloading: {url}', DownloadWarning)