Met Office Cardington: vertical wind profiles and backscatter measurements from Halo Doppler Lidar unit 30, 2011-2022

The Met Office Observation-based research Boundary Layer Facility, at the semi-rural field site (18 Ha) of Cardington (52° 06′ N, 00° 25′ W, 29 m ± 1 m amsl) in central-southern England between 2004 and 2024, operated three Halo Photonics Streamline Doppler lidars, denoted by unit numbers 01, 30 and 35. This dataset covers data from unit 30.

All three Halo systems were based on a 1565 nm laser emitting linearly polarized pulsed light through an 8 cm diameter lens with a heterodyne detector. Laser beam returns from the atmosphere are range-gated velocity and back-scattered power. The Halo systems are capable of full hemispheric scanning of the backscatter coefficient and radial velocity as a function of beam range.

The usual operation at Cardington was vertical stares (zenith angle=0°) with periodic wind scans that invoked various options of off-axis views. Wind profiles performed every 30 min was the default operation for wind scans. Most profiles of horizontal wind within the dataset are based on DBS (Doppler beam swinging) scans which use a tri-axis azimuthally orthogonal technique using the single lidar beam to retrieve horizontal mean wind components. This scan was chosen for the bulk of the time because it only takes about 21 s to complete, which leaves 98% of the available time to vertical stares if one wind scan is completed every 30 min. More recent scans in the dataset have used multi-axis VAD (velocity azimuth display) scans, which are a more involved version of the DBS scans and use 6 or 12 point off-zenith views. The vertical stares, DBS and VAD wind scans produced separate archived netCDF files.

Although depolarisation capability was possible with #35, this was only switched on occasionally during certain weather conditions.

A full list of NetCDF variables can be found in “A continuous hydrometeorological record (2004–2024) at the Met Office surface site of Cardington, UK.” Osborne et al. (2025). This paper should be referenced in any research/publications pertaining to this dataset.

To ensure optimal traceability and transparency of data, comprehensive metadata is included.