Characteristics of Tropical-Cyclone Turbulence and Intensity Predictability

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 similar to 9 hr and similar to 18 hr 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.