A Description of the MYNN Surface-Layer Scheme

The surface-layer scheme described here was originally developed for the Mellor–Yamada– Nakanishi–Niino (MYNN)-Eddy Diffusivity-Mass Flux (EDMF) scheme (Nakanishi and Niino 2009, Olson et al. 2019) within the Advanced Research version of the Weather Research and Forecasting Model (WRF-ARW) (Skamarock et al. 2019). Earlier versions of this scheme have been used in NOAA’s operational Rapid Refresh (RAP; Benjamin et al. 2016) and High-Resolution Rapid Refresh (HRRR) forecast systems since 2014. During this time, the scheme has undergone significant development in tandem with other components in the RAP/HRRR forecast systems. More recently, several new features have been added in order to accommodate different capabilities in the Common Community Physics Package (CCPP) (Firl et al. 2020), which is integrated with the FV3 model (Harris et al. 2020). This new version of the surface-layer scheme is a candidate to be used in the Rapid Refresh Forecast System (RRFS), which is a component of NOAA’s emerging Unified Forecast System, and a successor to the RAP/HRRR forecast systems.