ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa


Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2017, Vol. 14, No. 4, pp. 213-222

Cloud-resolving numerical analysis of the process of helicity generation in conditions of tropical cyclogenesis

G.V. Levina 1 , N.N. Zolnikova 1 , L.A. Mikhailovskaya 1 
1 Space Research Institute RAS, Moscow, Россия
Accepted: 21.06.2017
DOI: 10.21046/2070-7401-2017-14-4-213-222
A numerical analysis of the process of helicity generation in the tropical atmosphere of the Earth was carried out. The study was performed based on post-processing of the American data of cloud-resolving numerical simulation of tropical cyclones obtained by using the model RAMS — Regional Atmospheric Modeling System (Montgomery et al., 2006). A mechanism is discussed that generates the vertical vorticity and helicity in the tropical atmosphere due to the interaction of cloud convection with vertical shear of horizontal velocity. In connection with the fact that in all known examples of large-scale instabilities found in helical turbulent media there existed excitation thresholds depended on helicity magnitude, in this work, close attention is paid to the influence of the initial conditions on helicity generation during the first hours of the experiments. Helical flow characteristics were calculated and compared for two numerical experiments, in one of which an initial weak large-scale vortex disturbance was specified in the middle troposphere while in the other, the initial vortex was absent. The discussion is offered for the influence on helicity generation of a local heating at low levels of the troposphere, which was applied during the initial 300 seconds of experiments in order to accelerate development of cloud convection. Considered a process of generation by the local heating of a single intense helical cloud structure — the vortical hot tower (VHT), that reached its maximal intensity within the first 1-2 hours. Quantitative analysis of helicity generation by the single VHT was carried out for two different scenarios.
Keywords: tropical cyclogenesis, moist convective atmospheric turbulence, shear flow, helicity generation, cloud-resolving numerical analysis
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