| Summary: | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Coastal and Marine Systems Science. The Global Electric Circuit (GEC) of the atmosphere is a naturally occurring phenomenon in which the Earth’s atmosphere acts as a leaky capacitor between the Ionosphere and the Earth’s surface. Primarily due to the constant presence of thunderstorms and electrified clouds around the globe, the leaky capacitor is continually recharged by the upward storm current produced above thunderstorms and electrified clouds. The balance between the fair-weather return current which drains the circuit, and the input from the upward storm current creates the stable Earth’s electrical system known as the GEC. Under the changing climate, it is anticipated the GEC would vary accordingly. To understand the changes of global thunderstorms, a novel approach at observing thunderstorm trends is conducted by combining a 43-year ground station thunder day dataset with shorter-term satellite optical flash data from the Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS). A regional relationship between the thunder day occurrence and the lightning flash density as well as thunderstorm population is conducted in each global 5oxo5 grid. In many regions of the globe such as Argentina, China, and the Maritime Continent, a statistically significant agreement (r-value >0.8) is present between the simultaneous 16-year trends of all three explored variables. This indicates that in these regions, the thunder day recordings statistically represent the flash density and number of thunderstorm events. However, in other regions of the globe, the long-term changes of thunder day occurrence and flash density are not well correlated, or even negatively correlated, indicating the regional nature of the relationship between the two variables. With the understanding that thunderstorm activity is indeed changing over the course of the past several decades, it emphasizes the ...
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