Comparison of high-resolution simulations over increasingly complex terrain for wind energy applications
Abstract
In this work, we examine the performance of a mesoscale atmospheric model using very high horizontal resolution for wind power forecasting applications. We perform simulations at two wind farm sites in Western North America, one with significantly more complex terrain than the other. Domains are refined from mesoscale to finer scales using grid nesting to adequately resolve terrain and turbulence in the atmospheric boundary layer. Results show that complex terrain can greatly influence results at various spatial resolutions. Over the simpler terrain site, the use of different turbulence models, increased vertical resolution or using one- vs. two-way nesting yields minimal differences in model results of wind speed, shear, direction, and turbulence. It appears that for this particular domain the key topographic features are adequately resolved at even the coarser resolutions, so that only changes to the physical representations of the model such as soil moisture, landuse, or topography have any significant effect on the simulation results. In contrast, over complex terrain, results prove to be quite sensitive to the particular model configuration, including grid resolution and nesting choices. Several challenges arise in the complex terrain case which requires more effort to address in the model configuration. For example, due to the model's terrain-following coordinates, the grid cells closest to the surface can become quite distorted over very steep terrain and lead to numerical instability. We explored options such as smoothing the terrain, increasing the spacing off the ground, or implementing some degree of damping of sound waves, of which the latter two methods proved most appropriate. Given proper model configuration, comparison with field observations of hub-height wind speed and direction is quite favorable at both wind farm sites and shows promise for improvements in wind forecasting over complex terrain sites. This study illustrates the need for care when simulating flow over complex terrain, and also shows that computational resources can be saved when working over simpler terrain since coarser resolutions are often adequate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMGC51J..04M
- Keywords:
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- 3307 ATMOSPHERIC PROCESSES / Boundary layer processes;
- 3329 ATMOSPHERIC PROCESSES / Mesoscale meteorology;
- 3355 ATMOSPHERIC PROCESSES / Regional modeling;
- 3323 ATMOSPHERIC PROCESSES / Large eddy simulation