Posters

Abstract

Accurate representation of atmospheric stability is crucial for modeling wind farm flow. However, from wind site assessment campaigns, only measured wind and temperature profiles may be available for the characterization of stability. Information on stability can be taken from mesoscale models, or extra instrumentation like sonic anemometers for turbulent flux measurement may be considered. GEO-NET Umweltconsulting GmbH operates a 200 m measurement mast near Hanover in Northern Germany. The mast is primarily used for lidar verification and complies with the respective IEC standards. The measurements provide an extensive database of wind and turbulence profiles combined with high resolution flux and temperature measurements from sonic anemometers, installed at infour heights (77, 117, 157, 197 m). The location of the mast in flat terrain ensures that the measurement is not influenced by orography. In this contribution, we present vertical wind speed profiles classified by measured stability in terms of Obhukov-Length. It is analyzed whether flux measurements from different heights lead to significant differences. We show how the available measurements can be used to advance the use of atmospheric stability in modelling microscale flow. As stability determination, as done at the verification mast, cannot typically be applied in site assessment campaigns. Therefore, it is of interest to investigate whether mesoscale model data can be used for classification. We compare the measured stability with WRF model simulations and evaluate the simulated wind and temperature profiles. Microscale models used in site assessment can simulate different stability situations, which are then weighted according to their frequency. However, it is not straightforward to adjust the model setup to obtain the desired stability and corresponding wind profiles. Therefore, the combination of measured profiles and stability can serve as a kind of calibration. We will demonstrate such a calibration with our microscale flow model FITNAH-3D. We also investigated whether WRF data is suitable for estimating the weighting factors for the different microscale simulation cases. The measurement data from the commercially operated mast is intended to serve scientific purposes, and research initiatives are welcome.