Kinematic and microphysical evolution of the 29 June supercell observed during STEPS
Date
2003
Authors
Tessendorf, Sarah A., author
Rutledge, Steven A., author
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Abstract
The focus of this thesis is to examine the kinematic and microphysical properties of a severe storm using polarimetric and Doppler radar data. The data were collected during the Severe Thunderstorm Electrification and Precipitation Study (STEPS) that took place between 17 May 2000 and 20 July 2000 in eastern Colorado and western Kansas. One goal of STEPS is to find a relationship between the microphysics and kinematics of severe storms on the High Plains and their unusual positive cloud-to ground lightning production. The severe storm observed on 29 June 2000 produced large hail, frequent positive cloud-to-ground lightning, an F1 tornado, and displayed characteristic storm splitting evolution during the sampling period. Unprecedented measurements from three Doppler radars were used to describe the kinematics and rnicrophysics of this storm. Radial components of the wind fields relative to the three Doppler radars were combined to produce the three-dimensional winds in the storm. Bulk precipitation types (e.g., rain, hail) were objectively determined using the multi parameter variables available on two of the radars. The Doppler-derived kinematic fields were compared with the microphysical classifications over a nearly three-hour period to examine trends during the lifecycle of the supercell. Results showed that the supercell intensified rapidly while storm splitting occurred. Prior to splitting, there was little cloud-to-ground lightning and little evidence of hail aloft. After storm splitting. hail volume and cloud-to-ground lightning activity quickly intensified. The updraft of this storm pulsated, with maximum speeds to nearly 50 m s·1. The peaks in hail production aloft, largely around -10° C, were well correlated with the updraft fluctuations as well as with peaks in the frequency of positive cloud-to ground lightning flashes. These results are consistent with experimental work that shows positive charging in ice-ice collisions around -10° C. The dynamics of the storm-splitting process, in terms of radar-derived updraft and vorticity fields, were shown to be consistent with current conceptual models. The results of this thesis advance our knowledge of supercell evolution and will be used to help determine the electrification mechanisms of severe storms that produce predominantly positive cloud-to-ground lightning.
Description
Spring 2003.
Also issued as Sarah A. Tessendorf's thesis (M.S.) -- Colorado State University, 2003.
Also issued as Sarah A. Tessendorf's thesis (M.S.) -- Colorado State University, 2003.
Rights Access
Subject
Severe storms -- Doppler radar