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Characteristics of convective cells over the coastal regions of southeast Texas
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Vertical profiles of radar reflectivity and cloud-to-ground lightning characteristics associated with convective cells were analyzed for mesoscate systems occurring over the coastal regions of southeast Texas during the spring and summer months of 1993, 1994, and 1996. Radar and satellite data along with synoptic forcing information derived from standard surface charts were used to classify the mesoscale organization and evolution stage of each convective episode. Distinct differences in the internal structure of mature convective systems as evident by mixed-phase region reflectivity lapse rates and cloud-to-ground lightning comparisons were found for events of varying mesoscaic; organization. Focusing on sea breeze convection, it was shown that lightning initiation occurs once a cloud electrification threshold based upon maximum reflectivity as well as reflectivity decline in the mixed-phase region was met. The strength of mature convective storm cells was significantly different depending on the stage of evolution of the storm system. During the dissipating stages of the storm system, new cells were repeatedly formed, but they did not carry high reflectivity very far above the freezing level. This implied a decrease in the vertical depth and strength of the convective updrafts within the storm system and was well correlated with the discrepancy in-to-ground lightning between mature and dissipating storm systems. Differences in convective strength between midlatitude and tropical convection occurring in southeast Texas were also found when comparing radar reflectivity profiles and lightning statistics. Results were similar to findings of previous investigators but convection considered tropical in southeast Texas was found to have appreciably higher reflectivities than deep tropical convection, especially below the freezing level. The transition from land to water apparently also affected the strength of convective cells associated with strongly organized systems in their mature stage of development. In general, the vertical profiles of radar reflectivity at mid-levels decreased most rapidly for cells found over the water. What is surprising is that the difference was so well marked over a relatively short spatial scale. It is speculated that the change is likely associated with a marked difference in boundary layer structure between the water and land. In all, given that more than 1800 mature convective cells have been analyzed, this study provides valuable insight to the usefulness of reflectivity profiles and cloud-to-ground lightning in helping to diagnose the vertical structure of convective cells. This has important implications for the Tropical Rainfall Measuring Mission.
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Includes bibliographical references: p. 109-113.
Issued also on microfiche from Lange Micrographics.
Robinson, Michael (1998). Characteristics of convective cells over the coastal regions of southeast Texas. Master's thesis, Texas A&M University. Available electronically from
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