2023-9-30 0:0:0
Toward Improved Understanding and Modeling of Boundary Layer Processes in Tropical Cyclones Using Large-Eddy Simulation
Coastal Hazards CH
Accurately predicting tropical cyclone (TC) intensity and structure is challenging, and a contributing factor is poor understanding and modeling of boundary layer turbulent processes in high-wind conditions. These processes have scarce observations, and existing planetary boundary layer (PBL) parameterizations in models are generally designed for low-wind conditions, pointing to the need for continuous development of PBL parameterizations for hurricane forecast models. Researchers are building upon their recent development of a modeling framework that combines a small-domain large-eddy simulation (LES) and dropsonde thermodynamic data (collected in mature hurricanes by NOAA aircraft) to study the turbulence characteristics in the TC boundary layer. This framework pioneers the way to evaluate and improve PBL schemes in hurricane conditions, and it was used to evaluate and improve the PBL scheme from NOAA’s Global Forecast System (GFS) and Hurricane Analysis and Forecast System (HAFS) models. Hindcasts of the 2021 hurricane season demonstrated that the improved PBL scheme improves both intensity and structure forecasts. To transition their research to operations (R2O), they plan to incorporate the improved PBL scheme into the new version of HAFS, and the 2022 real-time HAFS forecasts will be available at They will also use the improved PBL scheme to assess the role of PBL parameterizations for Hurricane Michael (2018), which was stronger than projected. They recommend TKE-based PBL schemes for TC simulations based on the evaluation results and comparison to observations. Their recent findings highlight the role of advection of subgrid turbulence-kinetic-energy (TKE) in TC intensity and structure changes.