Wind climate in Yukon mountainous terrain

To quantify its wind energy potential the wind climate of the mountainous Yukon has been examined through data analysis and numerical modelling. Using many surface climate stations and radiosondes it was determined that the region's atmosphere is generally stably stratified, causing air to flow horizontally around mountain obstacles. The mesoscale model MC2, a non-hydrostatic and compressible model, has been used to simulate the mean wind climate of the steep mountainous Yukon with the intent to produce a reliable wind energy map. Early results of full scale simulations initialized with the standard NCEP/NCAR Reanalysis provided erroneous results for wind speeds and directions when compared to measurements. A detailed assessment of the mountainous Whitehorse Area climate provided insight into the expected flow behavior that MC2 should attain. It was clear that the atmosphere is generally stably stratified, valley inversions are common, and that the upper-level winds are often de-coupled from the valley winds. It was also found that downward momentum transfer and horizontal pressure gradients play important and varying roles that are dependent on the atmospheric stratification and valley orientation. With the new findings the Whitehorse area was simulated, again with MC2, but using simplified boundary conditions to compare the traditional method of running MC2 with an improved one. It was shown that the method by which the Reanalysis is used produces problematic pressure gradient directions in weak stratification. The modified input climate state attempts to correct this problem without modifying the present internal settings of MC2. It was found that in MC2 the horizontal pressure gradient terms provide the proper forcings to move air within deep valleys. However, MC2 in its present form produces excessively strong winds on lee slopes, contrary to measurements made in the Whitehorse Valley. The MC2 model may be improved by implementing a z-coordinate system, and redefining the Reanalysis inputs, particularly those sections of the input that are below the mountaintops of the model domain. With these improvements the MC2 model should be further tested to determine whether it is reliable tool for wind energy assessment in steep mountainous terrain.