8.3 WRF
Diffusion in Complex Terrain
Mass, Cliff, and David Ovens, University of Washington
When the WRF model is run at high resolution in complex
terrain, the model surfaces are substantially inclined, resulting in
substantial vertical mixing when diffusion is computed on coordinate
surfaces. WRF offers a
number of diffusion options, including second order diffusion on model or
horizontal surfaces, and the ability to use 6th order diffusion on model
surfaces. This talk will describe
the impacts of various diffusion options on a challenging situation; gap flow
inside and exiting the Columbia River Gorge of Oregon/Washington. It is shown that the choice of
diffusion option has a large impact of the fidelity of the gap flow and of
precipitation type. Further
experiments were completed for other cases and for extended seasonal
situation, and the results will be discussed in this talk. The hope is that these results will
help guide other users in making choosing diffusion options in the modeling
system, particularly in areas in or near terrain. |