Abstract
Jupiter on Earth, or Turbulence of Tropical Cyclones: from Peristrophic to Zonostrophic
Boris Galperin
University of South Florida St. Petersburg
Cyclostrophic rotation imprints a distinct signature upon turbulence structure of tropical
cyclones. Its intensity is characterized by the radius of maximum wind, Rm, and the
azimuthal wind velocity at that radius, Um. The corresponding cyclostrophic Coriolis
parameter, 2 Um/Rm, far exceeds its planetary counterpart for all storms and its impact
increases with storm intensity. The storm vortex can be thought of as a system
undergoing a superposition of planetary and cyclostrophic rotations represented by the
effective Coriolis parameter. In the classical Rankine vortex model, the inner region
undergoes solid-body rotation, rendering cyclostrophic Coriolis parameter constant.
However, data shows that this parameter deviates from a constant value and in the first
approximation, it can be represented by a linear term. This term is quantified in terms of
a cyclostrophic ß that gives rise to a cyclostrophic ß-effect that sustains vortex Rossby
waves. Horizontal turbulence in this system is quantified by one-dimensional,
longitudinal and transverse spectra computed along the radial direction. The evolution
of turbulence regimes in a system featuring increasing cyclostrophic effects progresses
from Kolmogorov to peristrophic to zonostrophic. Terrestrial oceanic and atmospheric
turbulence generally belongs in the peristrophic regime. Good qualitative and
quantitative agreement between the theoretical and observational spectra estimated
using a comprehensive database of tropical cyclone winds collected by reconnaissance
airplanes reveals that with increasing storm intensity, the cyclostrophic turbulence of
tropical cyclones evolves from purely peristrophic to mixed peristrophic-zonostrophic to
predominantly zonostrophic. The latter is analogous to the flow regime harboring zonal
jets on fast rotating giant planets featuring a strong planetary ß-effect.
cyclones. Its intensity is characterized by the radius of maximum wind, Rm, and the
azimuthal wind velocity at that radius, Um. The corresponding cyclostrophic Coriolis
parameter, 2 Um/Rm, far exceeds its planetary counterpart for all storms and its impact
increases with storm intensity. The storm vortex can be thought of as a system
undergoing a superposition of planetary and cyclostrophic rotations represented by the
effective Coriolis parameter. In the classical Rankine vortex model, the inner region
undergoes solid-body rotation, rendering cyclostrophic Coriolis parameter constant.
However, data shows that this parameter deviates from a constant value and in the first
approximation, it can be represented by a linear term. This term is quantified in terms of
a cyclostrophic ß that gives rise to a cyclostrophic ß-effect that sustains vortex Rossby
waves. Horizontal turbulence in this system is quantified by one-dimensional,
longitudinal and transverse spectra computed along the radial direction. The evolution
of turbulence regimes in a system featuring increasing cyclostrophic effects progresses
from Kolmogorov to peristrophic to zonostrophic. Terrestrial oceanic and atmospheric
turbulence generally belongs in the peristrophic regime. Good qualitative and
quantitative agreement between the theoretical and observational spectra estimated
using a comprehensive database of tropical cyclone winds collected by reconnaissance
airplanes reveals that with increasing storm intensity, the cyclostrophic turbulence of
tropical cyclones evolves from purely peristrophic to mixed peristrophic-zonostrophic to
predominantly zonostrophic. The latter is analogous to the flow regime harboring zonal
jets on fast rotating giant planets featuring a strong planetary ß-effect.
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