11 April 2005, in final form 13 December 2005 | SONG-YOU HONG and YIGN NOH, JIMY DUDHIA
This paper proposes a revised vertical diffusion package for the planetary boundary layer (PBL) that explicitly treats entrainment processes. The new scheme, named the Yonsei University PBL (YSU PBL), is developed to improve the performance of the Medium-Range Forecast (MRF) PBL scheme, which has been widely used in weather forecasting and climate models. The YSU PBL scheme includes an explicit treatment of entrainment at the top of the PBL, addressing issues such as excessive mixing in strong winds and under-mixing in convection-dominated conditions. The scheme is implemented in the Weather Research and Forecast (WRF) model and evaluated through one-dimensional offline tests and real-time forecasts.
The YSU PBL scheme is found to enhance boundary layer mixing in thermally induced free convection and reduce it in mechanically induced forced convection, improving the realism of the PBL structure. It also resolves the problem of excessive mixing in strong winds and the under-mixing in convection-dominated conditions. In a case study of a frontal tornado outbreak, the YSU PBL scheme better captures the convective inhibition and reduces widespread light precipitation ahead of the front, demonstrating its improved ability to reproduce large-scale features.
The YSU PBL scheme has been successfully integrated into the WRF model and has shown robust and realistic behavior in various situations since its inclusion in 2003. Systematic verifications and applications in high-resolution domains have further validated its effectiveness. The YSU PBL scheme is a promising option for mesoscale models, offering significant improvements over the MRF PBL scheme.This paper proposes a revised vertical diffusion package for the planetary boundary layer (PBL) that explicitly treats entrainment processes. The new scheme, named the Yonsei University PBL (YSU PBL), is developed to improve the performance of the Medium-Range Forecast (MRF) PBL scheme, which has been widely used in weather forecasting and climate models. The YSU PBL scheme includes an explicit treatment of entrainment at the top of the PBL, addressing issues such as excessive mixing in strong winds and under-mixing in convection-dominated conditions. The scheme is implemented in the Weather Research and Forecast (WRF) model and evaluated through one-dimensional offline tests and real-time forecasts.
The YSU PBL scheme is found to enhance boundary layer mixing in thermally induced free convection and reduce it in mechanically induced forced convection, improving the realism of the PBL structure. It also resolves the problem of excessive mixing in strong winds and the under-mixing in convection-dominated conditions. In a case study of a frontal tornado outbreak, the YSU PBL scheme better captures the convective inhibition and reduces widespread light precipitation ahead of the front, demonstrating its improved ability to reproduce large-scale features.
The YSU PBL scheme has been successfully integrated into the WRF model and has shown robust and realistic behavior in various situations since its inclusion in 2003. Systematic verifications and applications in high-resolution domains have further validated its effectiveness. The YSU PBL scheme is a promising option for mesoscale models, offering significant improvements over the MRF PBL scheme.