Abstract
The evolution of quasi-stationary spiral bands of vorticity, on the periphery of an initially symmetrical tropical-cyclone-like vortex moving on a β-plane, is investigated using a semi-spectral nondivergent nonlinear barotropic numerical model, formulated in a cylindrical coordinate system moving with the vortex. the results obtained with the numerical model are supported by analytic solutions of the linear barotropic vorticity equation in a moving frame of reference. The analysis of the model data shows the slow evolution and vortex-relative translation of a spectrum of Rossby waves, forming cyclonically curved spiral bands of positive and negative vorticity anomalies in the rear-right quadrant of the moving vortex. the analytic solutions of the linear barotropic vorticity equation and examination of the vorticity tendency in the numerical model indicate that the generation of the spiral bands is mainly a result of the vortex drift and the advection of planetary vorticity by the vortex wind field. Investigation of the kinematical structure of the trailing spiral bands of vorticity and their vicinity suggests that the cyclonic spiral bands in the numerical model may be related, either directly or indirectly, to the existence of quasi-stationary principal spiral bands of convection in real tropical cyclones.
Published Version
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