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The main focus of this thesis is to reveal the severe impact of the lower atmosphere on the middle/upper atmosphere environment. Especially for the thunderstorm system in the lower atmosphere, the caused effects of middle/upper atmosphere not only includes the energy deposition of the mechanical wave but also involves the electromagnetic coupling process. Lightning activity in a thunderstorm may cause the middle atmospheric discharge phenomena associated with the occurrence of sprites.
In this thesis, we studied an unusual event with sprites, lighting activity and gravity wave which is generated by a storm over Bangladesh on Apr 28, 2014, and investigated the thunderstorm-generated gravity wave and the electric-coupling process between the lower atmosphere and the middle/upper atmosphere.
To date, the detailed relationships among gravity waves, lightning, and sprites generated by the thunderstorm have rarely been documented in the scientific literature. For the unusual event over the Himalayan region on Apr 28, 2014, after analyzing the recorded sprites images, lightning data and weather satellite map, we improve our understanding of the whole process of thunderstorm produced gravity waves, lightning and sprites and their sequences.
The gravity wave (GW) is one of the fundamental dynamic processes in the atmosphere. The first step to understand the GW dynamics is to estimate the salient parameters of gravity waves since the propagation of atmospheric gravity waves from lower to middle/upper atmosphere may result in the modulation of emission intensities, especially for disturbance of OH and OI (557.7 nm) airglow layer.
All-Sky Imager is one of the important tools to observe the airglow modulation in the scientific community. However, an unusual event (Apr 28, 2014) with sprites, lighting activity, and gravity wave was recorded by an amateur photographer with a digital camera. The precise measurements of azimuthal/elevation angle and brightness were lacked.
The required analysis technique for precisely quantizing the GW parameters are different from the traditional method adopted in All-Sky Imager data. For geometry calibration, we utilized the precise location of the background stars to retrieve the geometry of the observed gravity waves. For brightness calibration, the apparent magnitude of recorded stars with considering atmosphere absorption are referenced to the modulated airglow intensity of GW. For wavelength length and GW period, we analyzed GW images with the Lomb-Scargle power spectrum. Our adopted analyses are validated through comparison of the obtained parameters of the gravity waves with the reports in the previous studies.
We developed the analyzing techniques for the recorded airglow images with improving the accuracy of geometry and intensity. The developed method is practical and useful especially for a low-cost, portable and highly mobile for All-Sky Imager observation in Taiwan. | en_US |