Seasonal Dependence of the Sensitivity of Simulated Wind Speed to Parameters Applied in the MYNN Boundary-Layer and MM5 Surface-Layer Schemes Over the WFIP2 Domain

The sensitivity of simulated hub-height wind speed to selected parameters in the Mellor-Yamada-Nakanishia-Niino (MYNN) boundary-layer and MMF surface-layer parameterizations are investigated using advanced uncertainty quantification (UQ) techniques. In this study, parameter values used within both schemes implemented in the Weather Research and Forecasting (WRF) model are varied over realistic ranges and differences in the hub-height wind speed are analyzed. In a previous study, focused on springtime conditions during May 2011, the most important parameters were found to be those related to the dissipation rate of turbulence kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and von Karman constant. In particular, the sensitivity to various constants applied in the calculation of the turbulent length scales were found to be dependent on the static stability. A second set of 256 simulations has been completed for February 2011 over the same domain and UQ techniques identical to those used for the springtime case have been applied. Overall, the results between the two periods are consistent and most differences are associated with an increased frequency of stable conditions during the wintertime. The largest seasonal differences are those associated with changes in the sensitivity as a function of terrain slope.