A Multiscale Numerical Study of Hurricane Andrew (1992). Part V: Inner-Core Thermodynamics

Abstract

Although considerable progress has been made in understanding the development of hurricanes, our knowledge of their three-dimensional structures of latent heat release and inner-core thermodynamics remains limited. In this study, the inner-core budgets of potential temperature (), moisture (q), and equivalent potential temperature (e) are examined using a high-resolution (⌬x ϭ 6 km), nonhydrostatic, fully explicit simulation of Hurricane Andrew (1992) during its mature or intensifying stage.It is found that the heat energy is dominated by latent heat release in the eyewall, sublimative-evaporative cooling near the eye-eyewall interface, and the upward surface fluxes of sensible and latent heat from the underlying warm ocean. The latent heating () rates in the eyewall range from less than 10ЊC h Ϫ1 to greater than 100ЊC h Ϫ1 , depending upon whether latent heat is released in radial inflow or outflow regions. The latent heating rates decrease inward in the inflow regions and become negative near the eye-eyewall interface. It is shown that the radial advective cooling in the inflow regions accounts for the initiation and maintenance of the penetrative downdrafts at the eye-eyewall interface that are enhanced by the sublimative-evaporative cooling. It is also shown that the vertical advection overcompensates the horizontal advection for the generation of the warm-cored eye, and the sum of latent heating and radial advective warming for the development of intense cooling in the eyewall. The moisture budgets show the dominant upward transport of moisture in the eyewall updrafts (and spiral rainbands), partly by the low-level outflow jet from the bottom eye regions, so that the eyewall remains nearly saturated.The e budgets reveal that e could be considered as an approximately conserved variable in the eyewall above the boundary layer even in the presence of deposition-sublimation and freezing-melting. The development of higher-e surfaces at the eye-eyewall interface is discussed in the context of deep convection, the e gradient and the mass recycling across the eyewall. It is concluded that the simulated hurricane is thermodynamically maintained by the upward surface flux of higher-e air from the underlying warm ocean, the descent of highere air in the upper troposphere along the eye-eyewall interface, and the recycling of some warmed-eye air at the eye-eyewall interface.

Impacts of Ice Phase Processes on Tropical Cyclone Development

“…The melting and sublimation of snow and graupel largely change the vertical profile of cooling between 4-7 km from that in the warm-rain experiment. The features of each heating rate of the ice-phase processes are similar to those obtained in the numerical simulation of Hurricane Andrew (Zhang et al 2002).…”

Effects of assimilating precipitation zones derived from satellite and lightning data on numerical simulations of tropical-like Mediterranean storms

“…In almost all other sectors of the storm, convective instability reaches 550 hPa and thus favours the formation of deep convection. This structure of convective instability would confirm the tropical-like characteristics of the medicanes (with similarities with hurricanes Emanuel, 1986;Zhang et al, 2002). In general, there is a light correlation between low/high central pressure centres and strong/weak horizontal winds (see Figs.…”

A Lagrangian Trajectory View on Transport and Mixing Processes between the Eye, Eyewall, and Environment Using a High-Resolution Simulation of Hurricane Bonnie (1998)

“…Maximum w increases from 1.2 to nearly 2.3 m s Ϫ1 through the period t ϭ 15-20 h. The distribution of e air (Fig. 4c, following Bolton 1980) suggests a reservoir of high e in the boundary layer of the eye that is characteristic of mature hurricanes (W98; Zhang et al 2002). In the eye, the maximum in e is greater than 376 K near the surface and reaches a minimum at z ϭ 4 km.…”