The impacts of effective diffusion on the axisymmetrization process

The dynamics of vortex axisymmetrization from the perspective of thermal anomalies is investigated using an idealized, nonlinear atmospheric model. Attempts at reproducing the results of previous work (Nolan and Grasso 2003; NG03) revealed a discrepancy with the impacts of purely asymmetric forcing. The current study finds that linear, thermal asymmetries can have an important, largely positive role on the vortex intensification whereas NG03 find nearly the opposite. Absolute angular momentum budgets reveal that the likely reason for the differences with NG03 is the strength of the basic-state secondary circulation. Radial momentum budgets and sensitivity analysis further reveals that differences in effective diffusion between the two nonlinear models is likely the driving force behind these results.

Reference: Nolan, D.S., and L.D. Grasso, 2003: Three-dimensional, nonhydrostatic perturbations to balanced, hurricane-like vortices. Part II: Symmetric response and nonlinear simulations. J. Atmos. Sci., 60, 2717-2745