2.2 Improvements to Low-Level Wind Forecasts in Complex Terrain from WFIP2

Monday, 8 January 2018: 10:45 AM
Room 15 (ACC) (Austin, Texas)
Jaymes S. Kenyon, NOAA/ESRL and CIRES, Univ. of Colorado, Boulder, CO; and J. B. Olson, M. D. Toy, J. M. Brown, W. M. Angevine, M. Marquis, Y. Pichugina, A. Choukulkar, T. A. Bonin, R. Banta, L. Bianco, I. V. Djalalova, K. McCaffrey, J. M. Wilczak, K. Lantz, C. N. Long, S. Redfern, J. Sharp, J. McCaa, M. T. Stoelinga, E. P. Grimit, J. W. Cline, W. J. Shaw, J. K. Lundquist, K. A. Lundquist, B. Kosovic, P. A. Jimenez, L. K. Berg, and V. R. Kotamarthi

The Second Wind Forecast Improvement Project (WFIP2) is a multiagency venture aimed at improving low-level wind forecasts in regions of complex terrain for the benefit of wind-energy applications. To achieve this objective, major modifications were developed for the Mellor–Yamada–Nakanishi–Niino (MYNN) turbulence parameterization, a component of the RAP/HRRR physics suite in the WRF–ARW modeling framework. These modifications were intended to address frequent RAP/HRRR forecast-failure modes in the Columbia Basin; namely, high wind-speed biases associated with the premature erosion of low-level cold pools during the cold season, and low wind-speed biases within diurnally varying, thermal-trough-induced gap flows during the warm season. Other aspects of the WRF–ARW framework were also investigated, including horizontal (and 3D) mixing, and refinements to numerical methods.

Drawing upon in-situ measurements collected during the WFIP2 field campaign, the forecast improvements made during WFIP2 will be demonstrated. Results from single-run case studies and extended retrospective test periods will be presented, using forecasts from the RAP, HRRR, and 750-m nest, as well as forecasts from "cold start" WRF–ARW configurations. The path to operational implementation of RAP/HRRR model improvements will also be discussed. Finally, we will reflect on the unsolved modeling challenges of WFIP2 to motivate future RAP/HRRR physics development.

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