Preprints
https://doi.org/10.5194/gmd-2021-184
https://doi.org/10.5194/gmd-2021-184

Submitted as: development and technical paper 15 Sep 2021

Submitted as: development and technical paper | 15 Sep 2021

Review status: this preprint is currently under review for the journal GMD.

Model development in practice: A comprehensive update to the boundary layer schemes in HARMONIE-AROME cycle 40

Wim C. de Rooy1, Pier Siebesma1,2, Peter Baas2, Geert Lenderink1, Stephan de Roode2, Hylke de Vries1, Erik van Meijgaard1, Jan Fokke Meirink1, Sander Tijm1, and Bram van 't Veen1 Wim C. de Rooy et al.
  • 1Research & Development Weather and Climate models, Royal Netherlands Meteorological Institute, De Bilt, Utrecht, PO Box 201 3730AE, The Netherlands
  • 2Department of Geoscience & Remote Sensing, Delft University of Technology, Delft , Stevinweg 1, 2628CN, The Netherlands

Abstract. 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 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 new revised parametric descriptions provide not only an improved prediction 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.

Wim C. de Rooy et al.

Status: open (until 10 Nov 2021)

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Wim C. de Rooy et al.

Wim C. de Rooy et al.

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Short summary
This paper describes a comprehensive model update to the boundary-layer schemes. Because the involved parameterisations are all built on widely applied frameworks, the here described modifications are applicable to many NWP and climate models. The model update contains substantial modifications to the cloud, turbulence and convection schemes and leads to a substantial improvement on several aspects of the model, especially low cloud forecasts.