Characteristics of Tropical‐Cyclone Turbulence and Intensity Predictability
Chanh Kieu, Richard Rotunno
Abstract
Abstract This study examines the characteristics of tropical‐cyclone (T‐C) turbulence and its related predictability implications. Using the Fourier‐Bessel spectral decomposition for convection‐permitting simulations, it is shown that T‐C turbulence possesses different spectral properties in the azimuthal and radial directions, with a steeper power law in the radial‐wavenumber than that in the azimuthal‐wavenumber direction. This spectral difference between the azimuthal and radial directions prevents one from using a single wavenumber to interpret T‐C intensity predictability as for classical homogeneous isotropic turbulence. Analyses of spectral error growth for a high‐wavenumber perturbation further confirm that the spectral growth is more rapid for high azimuthal wavenumbers than for the radial wavenumbers, reaching saturation after ∼9 h r and ∼18 h r for the azimuthal and radial directions, respectively. This result highlights the key difficulty in quantifying T‐C intensity predictability based on spectral upscale error growth for future applications.