Date of Award
2021
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Atmospheric and Earth Science
Committee Chair
Lawrence D. Carey
Committee Member
John R. Mecikalski
Committee Member
Phillip M. Bitzer
Committee Member
Timothy J. Lang
Committee Member
Wiebke Deierling
Subject(s)
Thunderstorms--Argentina--Córdoba (Province), Atmospheric electricity, Lightning
Abstract
In the RELAMPAGO-CACTI field campaigns held in the Argentinian province of Cordoba from November 2018 to April 2019, multiple instrumentations were deployed to study thunderstorms that are among the most intense in the world. In this study, the charge structures within these thunderstorms are investigated, along with the conditions associated with each charge structure archetype such as meteorological conditions, cloud condensation nuclei concentration, and radar-inferred microphysical and kinematic processes. Tested conditions are thought to contribute to high liquid water contents in the mixed-phase layer, which induce positive charging of graupel and anomalous charge structure storms through the non-inductive charging mechanism. A priori, conditions that lead to warm rain growth suppression and small warm cloud depth residence time such as large cloud condensation nuclei concentration, small warm cloud depth, and strong updrafts were hypothesized to be associated with anomalous charge structure thunderstorms as it increases liquid water content in the mixed-phase layer. In order to retrieve the dominant charge structure of events, a new automated method that uses Lightning Mapping Array (LMA) flash datasets was developed and made publicly available. Anomalous storms in Central Argentina region were not as frequent as initially expected (13.3%), with similar frequency to Central U. S. and much lower than observed in Colorado. Anomalous charge structure thunderstorms were characterized by the presence of large cloud supercooled liquid water contents in the mixed-phase layer as inferred from radar observations of elevated reflectivity, hail and high density precipitation ice amounts, and were caused by dry low-level humidity and low freezing height that contributed to a smaller warm cloud depth when compared to normal storms, as initially expected. Contrary to the initial hypothesis, anomalous storms were found to be associated with lower cloud condensation nuclei concentrations than normal storms. Analysis of updraft proxies from different sources, such as radiosondes, reanalysis, and radar, led to inconclusive outcomes, as anomalous storms updrafts were not clearly stronger than normal storms updrafts. Finally, this study details the conditions associated with storms that presented a distinct charge structure not typically observed in U.S. storms, which is an enhanced positive charge layer at temperature levels warmer than -10°C, a negative charge layer aloft at mid-levels and a practically absent upper-level positive charge. These storms were characterized by weak inferred updrafts and higher liquid water content in the lower levels of the mixed-phase layer when compared to normal storms, both conditions contributing to dominant charging in the low to mid-levels of the storm.
Recommended Citation
Lisboa Medina, Bruno, "Charge structure in central Argentina thunderstorms : characterization and processes" (2021). Dissertations. 477.
https://louis.uah.edu/uah-dissertations/477