Toward a unified parameterization of three dimensional turbulent transport in high resolution numerical weather prediction models

In numerical weather prediction (NWP) models, horizontal and vertical turbulent mixing is parameterized separately within the dynamic solver of a model and by a one-dimensional standalone module outside the dynamic core. This method becomes problematic as model resolution increases to the gray zone of turbulence parameterization where three-dimensional (3D) anisotropic turbulence tends to generate inter-connected horizontal and vertical mixing that cannot be artificially separated. To remediate the problem, a 3D scale-aware (SA) turbulence scheme based on a generalized turbulence closure applicable across scales has been developed and implemented in the Hurricane Analysis and Forecast System (HAFS). Simulations of 11 Atlantic basin storms of 2024 show that the new scheme substantially improves HAFS’s forecasting skill for storms with hurricane strength, suggesting that an appropriate account for 3D anisotropic turbulent transport is important for track and intensity forecast of tropical cyclones and provides a venue for realistically representing sub-grid-scale turbulence in NWP.