Abstract.A numerical approach is substantiated for searching for the large-scale alpha-like instability in thermoconvective turbulence. The main idea of the search strategy is the application of a forcing function which can have a physical interpretation. The forcing simulates the influence of smallscale helical turbulence generated in a rotating fluid with internal heat sources and is applied to naturally induced fully developed convective flows. The strategy is tested using the Rayleigh-Bénard convection in an extended horizontal layer of incompressible fluid heated from below. The most important finding is an enlargement of the typical horizontal scale of the forming helical convective structures accompanied by a cells merging, an essential increase in the kinetic energy of flows and intensification of heat transfer. The results of modeling allow explaining how the helical feedback can work providing the non-zero mean helicity generation and the mutual intensification of horizontal and vertical circulation, and demonstrate how the energy of the additional helical source can be effectively converted into the energy of intensive large-scale vortex flow.
1.In this communication we present a novel diagno sis for tropical cyclogenesis by examining helical self organization of moist convective atmospheric turbu lence in rotating non homogeneous atmosphere. Our original research approach was based on near cloud resolving numerical simulation and allowed for the quantitative diagnosis of cyclogenesis when the pri mary and secondary circulations in a forming hurri cane vortex become linked by deep rotating cumulon imbus cores-Vortical Hot Towers (VHTs). It is shown here how the generated linkage makes the nascent vor tex a helical system and allows a positive energetic feedback between the circulations that, with adequate moisture fluxes from the underlying sea surface, pro vides a self sustaining amplification process of the sys tem scale circulation.The hot towers in the tropical atmosphere of the Earth were first described by Riehl and Malkus in 1958 [1] as horizontally small but intense cumulonimbus 1 The article was translated by the authors. convection cores that reached the tropopause, that in the tropics typically lies at least 15 km above sea level. Recently, in near cloud resolving numerical simula tions [2, 3] "vortical" hot towers (VHTs) were found and suggested to be fundamental building blocks of the tropical cyclone vortex. In this work, VHTs are regarded as vortical coherent structures that span more than half of the depth of the tropical troposphere. This definition of VHTs is in analogy with the rotating ther mals in rotating Rayleigh Bénard convection (see [3,4]). In contrast with [1], we consider the broader spec trum of such convective structures rather than empha sizing only the most intense updrafts, consistent with the revised definition of hot towers given in [5]. As it was noted in [6], VHTs are helical by definition because they contain coincident updrafts and veitical vorticity. An overview of modem knowledge on VHTs, including observational evidence, is presented in [7].In paper [3], a new scenario of tropical cyclogene sis was proposed which is based on self organization of moist convective atmospheric turbulence in a favor able tropical environment. The observed process of self organization highlighted a key role of VHTs, and was realized via multiple convective structure mergers, which were accompanied by an upscale vorticity growth and system scale convergence of absolute angular momentum about the nascent vortex's axis of circulation. The simulations [3] showed how, as a result of such flow evolution during about 24 hours, a Abstract-A novel diagnosis for tropical cyclogenesis is presented by examining helical self organization of moist convective atmospheric turbulence in a rotating, non homogeneous atmosphere. Our original research approach employed near cloud resolving numerical simulations, which allows quantitative diagnosis of cyclogenesis when the primary and secondary circulations in a forming hurricane vortex become linked by deep rotating cumulonimbus cores-Vortical Hot Towers (VHTs). It is shown here how the generated linkag...
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