A real-time WRF forecast during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program: Performance and evaluation with observations

One of the primary objectives of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program is to evaluate model performance in predicting synoptic and local flows over mountainous terrain and thus to improve predictability. In order to achieve this goal, during the fall of 2012 and spring of 2013, two field experiments were conducted over Dugway Proving Ground (DPG), Utah, with comprehensive observations collected of soil states, surface energy budgets, near-surface atmospheric conditions, and profiling measurements from multiple platforms (e.g., balloon, lidar, tower, etc.).

During both field experiments, a real-time forecast was performed at the University of Utah with a mesoscale community Weather Research and Forecasting (WRF) model at high resolution (~1 km horizontally), four times (at 00, 06, 18, and 24 UTC) a day. The purpose of this real-time forecasting was not only to support decision-making during the field program but also to provide a useful database to evaluate the WRF model's performance in predicting synoptic flows over mountainous terrain. During the field program, a series of 48-h forecasts were produced for over 200 forecast leading times and for all Intensive Observational Periods (IOPs) during September–October 2012 and May 2013. After the field experiments, these forecast results were compared with observations collected from the field experiments.

Preliminary comparison between the WRF forecasts and observations show notable biases, with diurnal variations in near-surface atmospheric conditions under quiescent cases and flow-dependent patterns in errors associated with transitions and strong synoptic forcing cases. More comparisons are in progress with available soil states, surface flux, and profile observations from multiple platforms. The ability of the WRF model to predict synoptic and local flows over complex terrain, error characteristics and sources, and deficiencies in model physical parameterizations will be diagnosed and commented on. Additional numerical experiments and data assimilation will also be suggested. Detailed results will be presented during the conference.