A First Examination of the Helical Nature of Tropical Cyclogenesis
Abstract
In this paper we conduct a novel investigation of tropical cyclone genesis and intensification from the perspective of helical features of atmospheric flows of different scales, which contribute to the organization of the cyclone. Using the data from a near cloud-resolving numerical simulation, helical characteristics of the velocity field are calculated and analyzed during a process of formation of tropical depression vortex and its subsequent intensification up to a mature hurricane stage. An evolution of large scale vortex instability is followed, which develops on the background of intense cloud moist convection. The instability progresses by merging of small scale helical convective structures and results in the formation of larger and more intense spiral vortices. Distributions of helicity, kinetic energy and enstrophy have been obtained. It has been discovered that the process is accompanied by a break of the reflection symmetry of three dimensional moist convective turbulence that is manifested in the generation of nonzero mean helicity. With such a break of symmetry a theoretical hypothesis is proposed to explain the self organization of atmospheric processes under specific features of helical turbulence, which provide an energy transfer from small scales structures to larger vortices. The goal of this collaborative Russian American investigation, which started recently, is a clarification of the role of helicity in tropical cyclogenesis and intensification.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2010
- Accession Number
- ADA554528
Entities
People
- G. V. Levina
- Michael T. Montgomery
Organizations
- Naval Postgraduate School