Assessment of Two Planetary Boundary Layer Schemes (ACM2 and YSU) within the Weather Research and Forecasting (WRF) Model

Abstract:

The Weather Research and Forecasting (WRF) model is a highly configurable numerical weather prediction system used in both research and operational forecasting applications. Rigorously testing select configurations and evaluating the performance for specific applications is necessary due to the flexibility offered by the system. The Developmental Testbed Center (DTC) performed extensive testing and evaluation with the Advanced Research WRF (ARW) dynamic core for two physics suite configurations with a goal of assessing the impact that the planetary boundary layer (PBL) scheme had on the final forecast performance. The baseline configuration was run with the Air Force Weather Agency’s physics suite, which includes the Yonsei University PBL scheme, while the second configuration was substituted with the Asymmetric Convective Model (ACM2) PBL scheme.

This presentation will focus on assessing the forecast performance of the two configurations; both configurations were run over the same set of cases, allowing for a direct comparison of performance. The evaluation was performed over a 15 km CONUS domain for a testing period from September 2013 through August 2014. Simulations were initialized every 36 hours and run out to 48 hours; a 6-hour “warm start” spin-up, including data assimilation using the Gridpoint Statistical Interpolation system preceded each simulation. The extensive testing period allows for robust results as well as the ability to investigate seasonal and regional differences between the two configurations. Results will focus on the evaluation of traditional verification metrics for surface and upper air variables, along with an assessment of statistical and practical significance.