[Dutch]

Downscaling of mesoscale wind fields

Detailed analyses and forecasts of the weather over the Netherlands are based on the XHIRLAM atmospheric model. XHIRLAM is a so-called mesoscale model, describing the weather on a grid with a mesh width of approximately 11km.

Various important users of weather information, such as coastal zone managers, aviation authorities and the wind energy industry, have expressed a need for more spatially detailed predictions, in particular concerning the behaviour of the wind. It is therefore being studied to what extent it is possible to derive very high resolution wind information from mesoscale numerical weather prediction models. The method used for this is called downscaling.

Downscaling within the HYDRA project

The first attempts at downscaling wind information have been made in the context of the HYDRA project. HYDRA aims at using wind observations from a limited number of climatological stations situated on land, to derive the behaviour of the wind climate over sea along the entire Dutch coast. The observations of the land stations are interpolated (or extrapolated) geographically, by means of a physical model of the atmospheric boundary layer and detailed topographical informations from GIS datasets. More details on this transformation method can be found here.

Downscaling of model wind fields to local prognoses

The downscaling method developed in the HYDRA project can also be used to transform the wind fields produced by a weather prediction model such as XHIRLAM to a grid with a finer mesh. KNMI has set up an experimental downscaling module by which highly detailed wind fields can be generated for the coastal waters of the province of Zeeland, and Lake IJssel, for use by Dutch water authorities. The mesh width of the downscaling grid is about 1km. The output of the downscaling module is now being validated extensively against available local wind observations. More details on this validation can be found here (Dutch only) . Examples of the wind fields generated by the downscaling module for the coastal waters of Zeeland can be found here (Dutch only).

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Climate Services Desk