Axisymmetric Tornado Simulations at High Reynolds Number

AMS Citation:
Rotunno, R., G. H. Bryan, D. S. Nolan, and N. A. Dahl, 2016: Axisymmetric Tornado Simulations at High Reynolds Number. Journal of the Atmospheric Sciences, 73, 3843-3854, doi:10.1175/JAS-D-16-0038.1.
Date:2016-10-01
Resource Type:article
Title:Axisymmetric Tornado Simulations at High Reynolds Number
Abstract: This study is the first in a series that investigates the effects of turbulence in the boundary layer of a tornado vortex. In this part, axisymmetric simulations with constant viscosity are used to explore the relationships between vortex structure, intensity, and unsteadiness as functions of diffusion (measured by a Reynolds number Re-r) and rotation (measured by a swirl ratio S-r). A deep upper-level damping zone is used to prevent upper-level disturbances from affecting the low-level vortex. The damping zone is most effective when it overlaps with the specified convective forcing, causing a reduction to the effective convective velocity scale W-e. With this damping in place, the tornado-vortex boundary layer shows no sign of unsteadiness for a wide range of parameters, suggesting that turbulence in the tornado boundary layer is inherently a three-dimensional phenomenon. For high Re-r, the most intense vortices have maximum mean tangential winds well in excess of W-e, and maximum mean vertical velocity exceeds 3 times W-e. In parameter space, the most intense vortices fall along a line that follows S-r similar to Re-r(-1/3), in agreement with previous analytical predictions by Fiedler and Rotunno. These results are used to inform the design of three-dimensional large-eddy simulations in subsequent papers.
Peer Review:Refereed
Copyright Information:Copyright 2016 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.
OpenSky citable URL: ark:/85065/d7hm5b4t
Publisher's Version: 10.1175/JAS-D-16-0038.1
Author(s):
  • Richard Rotunno - NCAR/UCAR
  • George H. Bryan - NCAR/UCAR
  • David S. Nolan
  • Nathan A. Dahl
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