Assessment of Planetary Boundary-Layer Schemes in the Weather Research and Forecasting Mesoscale Model Using MATERHORN Field Data

The study was aimed at understanding the deficiencies of numerical mesoscale models by comparing predictions with a new high-resolution meteorological dataset collected during the Mountain Terrain Atmospheric Modelling and Observations (MATERHORN) Program. The simulations focussed on the stable boundary layer (SBL), the predictions of which continue to be challenging. High resolution numerical simulations (0.5-km horizontal grid size) were conducted to investigate the efficacy of six planetary boundary-layer (PBL) parametrizations available in the advanced research version of the Weather Research and Forecasting model. One of the commonly used PBL schemes was modified to include eddy diffusivities that account for enhanced momentum transport compared to heat transport in the SBL, representing internal wave dynamics. All of the tested PBL schemes, including the modified scheme, showed a positive surface temperature bias. None of the PBL schemes was found to be superior in predicting the vertical wind and temperature profiles over the lowest 500 m, however two of the schemes appeared superior in capturing the lower PBL structure. The lowest model layers appear to have a significant impact on the predictions aloft. Regions of sporadic flow interactions delineated by the MATERHORN observations were poorly predicted, given such interactions are not represented in typical PBL schemes.