We present observations of a gravity wave (GW) event over the Netherlands and Belgium in the night and early morning of 30 June 2022. This event was captured by instruments that are part of the meteorological observational network of The Netherlands and Belgium, including the operational weather radars and automatic lidar ceilometers, and by the (tower) in situ and Doppler lidar at the Cabauw atmospheric research station. Together they provide 3D information on the GW event, with detailed information on the vertical profiles from Cabauw, and the spatial extent and evolution from the observational synoptic network. Two distinct GW trains were observed, both interpreted as ducted GW that are trapped in the lowermost 500 m of the stable nocturnal boundary layer. The GWs showed large vertical velocity amplitudes up to 3 m/s, resulting in strong modulations of wind, temperature, humidity and pressure. By comparing our observations to the Copernicus European Regional ReAnalysis (CERRA) wind and temperature fields, we interpret that these GWs were generated by convergence lines over Belgium and the North Sea that was linked to an occlusion front.

The parameterised description of subgrid-scale processes in the clear and cloudy boundary layer has a strong impact on the performance skill in any numerical weather prediction (NWP) or climate model and is still a prime source of uncertainty. Yet, improvement of this parameterised description is hard because operational models are highly optimised and contain numerous compensating errors. Therefore, improvement of a single parameterised aspect of the boundary layer often results in an overall deterioration of the model as a whole. In this paper, we will describe a comprehensive integral revision of three parameterisation schemes in the High Resolution Local Area Modelling - Aire Limitée Adaptation dynamique Développement InterNational (HIRLAM-ALADIN) Research on Mesoscale Operational NWP In Europe - Applications of Research to Operations at Mesoscale (HARMONIE-AROME) model that together parameterise the boundary layer processes: the cloud scheme, the turbulence scheme, and the shallow cumulus convection scheme. One of the major motivations for this revision is the poor representation of low clouds in the current model cycle. The newly revised parametric descriptions provide an improved prediction not only of low clouds but also of precipitation. Both improvements can be related to a stronger accumulation of moisture under the atmospheric inversion. The three improved parameterisation schemes are included in a recent update of the HARMONIE-AROME configuration, but its description and the insights in the underlying physical processes are of more general interest as the schemes are based on commonly applied frameworks. Moreover, this work offers an interesting look behind the scenes of how parameterisation development requires an integral approach and a delicate balance between physical realism and pragmatism.