Radiation

Instrumentation

The BCO is equipped with a solar and terrestrial radiation measurement station, comprised of 4 radiation sensors attached to a SOLYS2 sun tracker. The instruments were installed on 2015-03-30.

More specifically, the apparatus sits on the top of the BCO container, \(4.5\,\mathrm{m}\) above the ground, or \(21.5\,\mathrm{m}\) above mean sea level

The 4 sensors are as follows:

• shaded pyranometer mounted on table of sun tracker for diffuse radiation (CMP21 by Kipp and Zonen),

• non-shaded pyranometer mounted on table of sun tracker for diffuse radiation (CMP21 by Kipp and Zonen),

  pyranometers measure solar irradiance from a hemispherical field of view diffuse radiation is the portion of incoming shortwave (SW) radiation due to atmospheric scattering

• shaded pyrgeometer mounted on table of sun tracker for longwave (LW) radiation (CGR4 by Kipp and Zonen)

• pyrheliometer mounted on the side of the sun tracker (CPH1 by Kipp and Zonen) points directly into the sun.

Two sets of 4 sensors are used and exchanged simultaneously approximately every two years.

• Set 1: CMP21 #140337, CMP21 #140356, CGR4 #140034 (replaced by 220446), CHP1 #140059 (replaced by 160388)

• Set 2: CMP21 #160654, CMP21 #160653, CGR4 #150139, CHP1 #160388

The calibration is done by the DWD in Lindenberg, and the solar irradiance (\(\mathrm{W} \mathrm{m}^{-2}\)), the raw voltages, the sensitivities, and the housing temperatures of each of the 4 sensors are available.

Data Availability

Housekeeping data is available as .zarr files in the catalog as:

• BCO.radiation_c1 (2015-03-30 to 2015-10-14)

• BCO.radiation_c2 (2015-10-15 to present)

And a level 2 product is being tested and can be found under the catalog entry BCO.radiation (2015-03-30 to present). The level 2 product is filtered and quality controlled combining the following techniques: (1) pre-determined flags in the level 1 data with meanings high_anomaly, low_anomaly, or broken are dropped (2) for c2, we have access to recorded voltages and can therefore drop times when the irradiance measured is 0 but there is some nonzero voltage recorded (3) use ±4000 W m-2 as bounds (non-inclusive, because this is the maximum operational irradiance of the instrument itself) for unphysical measurements and drop all fluxes outside of these bounds.

import intake
import matplotlib.pyplot as plt

cat = intake.open_catalog("https://tcodata.mpimet.mpg.de/catalog.yaml")
ds = cat.BCO.radiation(time="PT1H").to_dask().sel(time="2024-09")
ds

/builds/tco/bco/docs/.venv/lib/python3.14/site-packages/intake_xarray/base.py:21: FutureWarning: The return type of `Dataset.dims` will be changed to return a set of dimension names in future, in order to be more consistent with `DataArray.dims`. To access a mapping from dimension names to lengths, please use `Dataset.sizes`.
  'dims': dict(self._ds.dims),

<xarray.Dataset> Size: 35kB
Dimensions:             (time: 720, bnd: 2)
Coordinates:
  * time                (time) datetime64[ns] 6kB 2024-09-01T00:30:00 ... 202...
    alt                 float64 8B ...
    lat                 float64 8B ...
    lon                 float64 8B ...
Dimensions without coordinates: bnd
Data variables:
    lw_down_diffuse     (time) float32 3kB dask.array<chunksize=(720,), meta=np.ndarray>
    raw_count           (time) float64 6kB dask.array<chunksize=(720,), meta=np.ndarray>
    sw_down_diffuse     (time) float32 3kB dask.array<chunksize=(720,), meta=np.ndarray>
    sw_down_global      (time) float32 3kB dask.array<chunksize=(720,), meta=np.ndarray>
    sw_down_suntracker  (time) float32 3kB dask.array<chunksize=(720,), meta=np.ndarray>
    time_bounds         (time, bnd) datetime64[ns] 12kB dask.array<chunksize=(720, 2), meta=np.ndarray>
Attributes:
    Conventions:      CF-1.12
    _cutoff_date:     2026-10-16T23:55:00.000001000
    bcoproc_version:  0.0.0.post2256.dev0+3c9a772
    institution:      Max Planck Institute for Meteorology, Hamburg
    license:          CC0-1.0
    location:         The Barbados Cloud Observatory (BCO), Deebles Point, Ba...
    platform:         BCO
    source:           https://swift.dkrz.de/v1/dkrz_948e7d4bbfbb445fbff5315fc...
    summary:          This dataset contains measurements of downwelling short...
    title:            Radiation data from BCO (Level 2)
    tool_versions:    {"Python": "3.14.3 (main, Mar  3 2026, 14:59:53) [Clang...

xarray.Dataset

• Dimensions:
  • time: 720
  • bnd: 2
• Coordinates: (4)
  • time
    (time)
    datetime64[ns]
    2024-09-01T00:30:00 ... 2024-09-...

    axis :

    T

    standard_name :

    time

    units_metadata :

    leap_seconds: utc

    array(['2024-09-01T00:30:00.000000000', '2024-09-01T01:30:00.000000000',
           '2024-09-01T02:30:00.000000000', ..., '2024-09-30T21:30:00.000000000',
           '2024-09-30T22:30:00.000000000', '2024-09-30T23:30:00.000000000'],
          shape=(720,), dtype='datetime64[ns]')

  • alt
    ()
    float64
    ...

    [1 values with dtype=float64]

  • lat
    ()
    float64
    ...

    [1 values with dtype=float64]

  • lon
    ()
    float64
    ...

    [1 values with dtype=float64]

• Data variables: (6)
  • lw_down_diffuse
    (time)
    float32
    dask.array<chunksize=(720,), meta=np.ndarray>

    cell_methods :

    time: mean

    long_name :

    Longwave downwelling diffuse radiation

    standard_name :

    surface_downwelling_longwave_flux_in_air

    units :

    W m-2

    Array Chunk Bytes 2.81 kiB 2.81 kiB Shape (720,) (720,) Dask graph 1 chunks in 3 graph layers Data type float32 numpy.ndarray

  • raw_count
    (time)
    float64
    dask.array<chunksize=(720,), meta=np.ndarray>

    cell_methods :

    time: sum

    Array Chunk Bytes 5.62 kiB 5.62 kiB Shape (720,) (720,) Dask graph 1 chunks in 3 graph layers Data type float64 numpy.ndarray

  • sw_down_diffuse
    (time)
    float32
    dask.array<chunksize=(720,), meta=np.ndarray>

    cell_methods :

    time: mean

    long_name :

    Shortwave downwelling diffuse radiation

    standard_name :

    surface_diffuse_downwelling_shortwave_flux_in_air

    units :

    W m-2

    Array Chunk Bytes 2.81 kiB 2.81 kiB Shape (720,) (720,) Dask graph 1 chunks in 3 graph layers Data type float32 numpy.ndarray

  • sw_down_global
    (time)
    float32
    dask.array<chunksize=(720,), meta=np.ndarray>

    cell_methods :

    time: mean

    long_name :

    Shortwave downwelling global radiation

    standard_name :

    surface_downwelling_shortwave_flux_in_air

    units :

    W m-2

    Array Chunk Bytes 2.81 kiB 2.81 kiB Shape (720,) (720,) Dask graph 1 chunks in 3 graph layers Data type float32 numpy.ndarray

  • sw_down_suntracker
    (time)
    float32
    dask.array<chunksize=(720,), meta=np.ndarray>

    cell_methods :

    time: mean

    long_name :

    Shortwave downwelling direct radiation

    standard_name :

    surface_direct_downwelling_shortwave_flux_in_air

    units :

    W m-2

    Array Chunk Bytes 2.81 kiB 2.81 kiB Shape (720,) (720,) Dask graph 1 chunks in 3 graph layers Data type float32 numpy.ndarray

  • time_bounds
    (time, bnd)
    datetime64[ns]
    dask.array<chunksize=(720, 2), meta=np.ndarray>

    Array Chunk Bytes 11.25 kiB 11.25 kiB Shape (720, 2) (720, 2) Dask graph 1 chunks in 3 graph layers Data type datetime64[ns] numpy.ndarray

• Attributes: (11)

  Conventions :

  CF-1.12

  _cutoff_date :

  2026-10-16T23:55:00.000001000

  bcoproc_version :

  0.0.0.post2256.dev0+3c9a772

  institution :

  Max Planck Institute for Meteorology, Hamburg

  license :

  CC0-1.0

  location :

  The Barbados Cloud Observatory (BCO), Deebles Point, Barbados, West Indies

  platform :

  BCO

  source :

  https://swift.dkrz.de/v1/dkrz_948e7d4bbfbb445fbff5315fc433e36a/airflow_production/BCO.radiation_x255960_0_PT10M.zarr

  summary :

  This dataset contains measurements of downwelling shortwave and longwave radiation measurements from sensors mounted on the table of a SOLYS2 sun tracker at the BCO.

  title :

  Radiation data from BCO (Level 2)

  tool_versions :

  {"Python": "3.14.3 (main, Mar 3 2026, 14:59:53) [Clang 21.1.4 ]", "toolz": "1.1.0", "fsspec": "2026.7.0", "pandas": "3.0.5", "certifi": "2026.7.22", "bcologs": "0.0.0.post2256.dev0+3c9a772", "numpy": "2.5.3", "frozenlist": "1.8.0", "locket": "1.0.0", "six": "1.17.0", "aiohappyeyeballs": "2.7.1", "propcache": "0.5.2", "wrapt": "2.4.0", "pygments": "2.21.0", "idna": "3.19", "partd": "1.4.2", "cftime": "1.6.5", "cloudpickle": "3.1.2", "multidict": "6.8.0", "ruff": "0.13.0", "dask": "2026.8.0", "platformdirs": "4.11.8", "zarr": "2.18.7", "python-dateutil": "2.9.0.post0", "pytest": "9.1.1", "MarkupSafe": "3.0.3", "click": "8.5.0", "iniconfig": "2.3.0", "pyyaml": "6.0.3", "aiohttp": "3.14.3", "netCDF4": "1.7.4", "tzdata": "2026.3", "packaging": "26.3", "asciitree": "0.3.3", "intake": "2.0.8", "aiosignal": "1.4.0", "bcoproc": "0.0.0.post2256.dev0+3c9a772", "netcdf4": "1.7.4", "scipy": "1.18.1", "jinja2": "3.1.6", "numpy_groupies": "0.11.3", "attrs": "26.1.0", "yarl": "1.24.5", "xarray": "2026.7.0", "datarecords": "0.0.0.post2256.dev0+3c9a772", "numcodecs": "0.15.1", "pendulum": "3.2.0", "networkx": "3.6.1", "flox": "0.11.2", "pluggy": "1.6.0", "deprecated": "1.3.1"}

Sample Plot

ds.sw_down_global.groupby(ds.time.dt.hour).mean().plot()
plt.xlabel("time / hour")
plt.title("diurnal cycle during 2024-09")

Text(0.5, 1.0, 'diurnal cycle during 2024-09')