Hurricane Coherent Turbulence Structure from Saildrone Uncrewed Surface Vehicle Observations

Tropical cyclones obtain and lose energy through turbulent processes at the air-sea interface. Thus, it is important to improve our understanding of these processes for improving intensity prediction. Numerical and observational studies have shown that coherent features such as eye-eyewall meso-vortices and rolls may have a significant impact on turbulent transfer in the hurricane boundary layer. However, the limited availability of observations near the air-sea interface has hindered efforts to improve our knowledge of coherent structure impacts. This study analyzes unprecedented high-frequency wind data collected by saildrone uncrewed surface vehicles to examine the characteristics of hurricane near-surface coherent features. Velocity spectra and co-spectra are derived to quantify dominant eddy sizes and their variations with wind speeds and radial locations. Effects of coherent structures on momentum transfer are evaluated. The results may offer useful guidance in numerical weather prediction efforts aimed at improving forecast of hurricane intensity. Because of the small sample size analyzed in this work, further analyses of the turbulent characteristics in the hurricane surface layer are imperative.