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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'The model chain: First steps towards tomorrow's technology' taking place on Thursday, 13 March 2014 at 09:00-10:30. The meet-the-authors will take place in the poster area.

Jens Kampmeyer anemos GmbH, Germany
Co-authors:
Jens Kampmeyer (2) F P Julia Bethke (2) Heinz-Theo Mengelkamp (2) Anselm Grötzner (3) Tobias Klaas (4) Lukas Pauscher (4) Doron Callies (4)
(1) anemos, Reppenstedt, Germany (2) anemos GmbH, Reppenstedt, Germany (3) CUBE engineering, Kassel, Germany (4) Fraunhofer IWES, Kassel, Germany

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Abstract

Extensive verificaton of mesoscale andCFD-model downscaling

Introduction

The amount of commonly used wind data for site assessment grows rapidly, but detailed and comprehensive verifications are rare. Here a high resolution mesoscale data set was created and verified with various measurements in Germany and Poland. Out of the simulated years 2011 and 2012 we separately focused on seasons dominated by large synoptic scales and seasons with strong convective climates for deeper analysis of atmospheric stability. A CFD-Model is used for detailed consideration of a hilly forest site.

Approach

Regionally distributed wind data measured with 120 high quality and certified anemometers, mounted on 40 masts with a height ranging from 30 to 200 m, are prepared for verification. With respect to these measurements the MERRA Reanalysis data turn out to be the best choice for further refinement. So WRF was scaled down to 3 km horizontal resolution. For the complex site CFD Simulations with Meteodyn WT were carried out to refine the mesoscale data.

Main body of abstract

In this study we evaluate the performance of the WRF mesoscale model in a broad range of environments. The following verification methods on hourly time based wind data identify benefits and short comings of the model in rotor affected heights. Vertical and diurnal profiles show the models performance in simulating shear and atmospheric stability. Frequency distributions of speed and direction, quantile-quantile diagrams and power spectra inform about the scales that are added to the driving data. The basic skill parameters correlation, mean absolute error and bias are analysed in annual cycles and present the seasonal deviations. A sensitivity study on horizontal grid resolution, for various complex sites, results in a critical grid size around 3 km which resolves scales containing the main part of kinetic energy. On a site with fine structured land surface the performance of the model with 3 km resolution decreases. Here the ability of a CFD model to better capture smaller scales generated by hilly and wooded terrain are verified with a 200 m measurement mast.

Conclusion

Due to using the large data base of wind measurements conducted in different surroundings, it was possible to conduct a meaningful verification of a modelled area-wide wind data base with a 3 km grid resolution for Germany and Poland. The resulting skill parameters show the models accuracy in wind resource estimation on sites with differing complexity and challenges.


Learning objectives
Presented is a detailed mesoscale and CFD model verification in a broad range of environments in Germany and Poland. For this area resulting model skills based on yearlong comparisons are derived. The advantages and short comings of the model are highlighted.