Improving Hurricane Boundary Layer Parameterization Scheme Based on Observations

Abstract

Abstract Flight‐level data and global positioning system dropwindsonde observations collected from more than 187 flights into 19 tropical cyclones were used to examine why different planetary boundary layer parameterization schemes applied to hurricane models produce diverse forecasts of structure and intensity change. Two popular, yet diverse, physics schemes, namely, the GFS K‐Profile and a 1.5‐order turbulence kinetic energy closure parameterization from NOAA's next‐generation FV3‐based Hurricane Analysis and Forecast System were used. It was found that uncertainty related to some key variables used in the parameterization of the eddy diffusivity, Km, led to diverse solutions. For a given grid resolution, both parameterization schemes converged to a similar forecast state provided those uncertainties could be identified and improved based on observations. This is important for providing a generalized framework for the development and evaluation of parameterization schemes in operational models that resemble reality. This study also indicates that the shape of the Km profile is equally important as its maximum value. The smaller the Km near the surface, the stronger the inflow in the boundary layer.

Keywords

• eddy diffusivity
• hurricane intensity
• hurricane structure
• PBL parameterization
• tropical cyclones
• turbulence kinetic energy