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Lightning location characteristics and vertical structure analysis of isolated storm cells in the TOGA COARE region
Abstract
Previous studies have investigated the difference in structure between continental and oceanic storms, and tropical versus mid-latitude storms. This is the first study that has investigated the differences in vertical structure between lightning producing storm cells, and non-lightning producing cells over the tropical oceans. The characteristics of lightning locations with respect to radar reflectivity were also examined. Lightning characteristics of flashes associated with TOGA COARE storm cells were examined. One hundred fifty-three flashes were detected by three direction finders within the study area, a 150 kilometer circle around the Vickers research vessel. Radar reflectivities and reflectivity gradients were compared to flash counts. It was found that lightning flashes tended to occur in the convective region (the region enclosed by the 30 dBZ contour) with a peak at 37 dBZ, but avoiding the highest reflectivity values. Flashes often occurred in reflectivity gradients higher than 3 dBZ/km at 2 and 5 kilometers, which is the likely position of an updraft-downdraft interface. Isolated storm cells from four days during TOGA COARE were analyzed. Mean vertical profiles of radar reflectivity (VPRR) were constructed; these profiles were compared with other VPRRs from other tropical oceanic storms, and tropical and mid latitude continental storms. Reflectivity lapse rates were found to be effective in discriminating between lightning and non-lightning storms. A connection between the amount of lightning flashes and characteristics of VPRRs was examined. It was found that lightning and non-lightning storm cell VPRRs were associated with lower reflectivity lapse rates than ever previously been found for tropical oceanic storms. Reflectivity lapse rate of the mean profiles of lightning storm cells was 3.32 dBZ/km versus the 4.33 dBZ/km found for non-lightning storms. Lightning storms had reflectivity lapse rates similar to 3.5 dBZ/km lapse rate of tropical continental storms studied by Zipser and Lutz (I 994). Lapse rates of non-lightning cells significantly exceeded lapse rates from other cells in different tropical oceanic regimes.
Description
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Citation
Barnaby, Stephen Andrew (1995). Lightning location characteristics and vertical structure analysis of isolated storm cells in the TOGA COARE region. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -B373.
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