Mountain wave structures occurring within a major orographic precipitation event: Part 2. Evaluation of mesoscale model simulations

Part 1 in this series of presentations, describes how airborne Doppler radar data were systematically collected over the windward and leeward slopes of the Oregon Cascades during an extended period on 13-14 December 2001. These observations provide a highly comprehensive, three-dimensional view of mesoscale airflow and precipitation structures uniquely suited for evaluating mesoscale model performance. The NCAR/PSU MM5 v3.6 and Weather Research and Forecasting (WRF) models were run at high resolution (grid spacing of 1.33-km) to simulate this event. Using these model runs and the IMPROVE-II observational data, a thorough analysis of the models' simulated kinematic and precipitation structures is conducted. Attention is focused on assessing the veracity of the models' depiction of the phase, amplitude and vertical extent of a standing mountain wave located over the mean crest of the Cascades, as well as multiple shorter-wavelength oscillations identified over the windward foothills. Model sensitivity studies focusing on the choice of boundary layer parameterization and its impact on simulated kinematic features (including an elevated shear layer) will be introduced. Additionally, a comparison of simulations using the MM5 and WRF models will be highlighted.