THE INFLUENCE OF BOUNDARY-LAYER SHEAR AND STATIC STABILITY ON LOW-LEVEL VERTICAL ACCELERATIONS IN A SUPERCELL
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Authors
Caulfield, Sean P.
Subjects
tornadoes
boundary layer
supercell
shear
static stability
boundary layer
supercell
shear
static stability
Advisors
Peters, John M.
Date of Issue
2018-12
Date
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
It is well documented that tornadoes are formed from a special breed of rotating thunderstorms called supercells, and that tornadogenesis is a result of several factors, one of which is the vertical stretching of low-level vorticity. Not as well understood are the factors that contribute to vertical acceleration of low-level vorticity in the updraft region of a supercell to support tornadogenesis. This paper examined the influence of combining both low-level shear and low-level static stability on low-level vertical accelerations using idealized simulation from Cloud Model 1 (CM1). A matrix of simulations varied the low-level shear and the low-level convective inhibition (CIN) in order to parse out the dynamic response of these parameters on the low-level forcing. When shear was added to simulations, there was a consistent positive response to the low-level dynamic forcing; when low-level CIN was increased, there was a consistent negative response to the low-level buoyant forcing. Despite the chaotic nature of a supercell environment, a balance can be achieved in the lower atmosphere where the low-level CIN can counteract the low-level shear and inhibit the vertical stretching of vorticity. Since this phenomenon is associated with tornadogenesis, a correlation can be made between the ratio of low-level static stability to low-level shear and its effect on tornado formation.
Type
Thesis
Description
Series/Report No
Department
Meteorology (MR)
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NPS Report Number
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.