| 研究生: |
林昱丞 Lin, Yu-Cheng |
|---|---|
| 論文名稱: |
深度學習應用於 ISUAL 事件辨識與高空短暫發光現象之時空特徵研究 Deep Learning for Identification and Spatiotemporal Analysis of Transient Luminous Events by ISUAL Observations |
| 指導教授: |
陳炳志
Chen, Alfred Bing-Chih |
| 學位類別: |
博士 Doctor |
| 系所名稱: |
理學院 - 物理學系 Department of Physics |
| 論文出版年: | 2026 |
| 畢業學年度: | 114 |
| 語文別: | 英文 |
| 論文頁數: | 178 |
| 中文關鍵詞: | 高空閃電事件 、福爾摩沙衛星二號 、ISUAL 、全球閃電偵測網路 、深度學習 、卷積神經網路 、DIAT |
| 外文關鍵詞: | FORMOSAT-2, Transient Luminous Events, ISUAL, WWLLN, DIAT, Convolutional Neural Networks, Deep Learning |
| 相關次數: | 點閱:7 下載:0 |
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搭載於福爾摩沙衛星二號(FORMOSAT-2)上的高空閃電影像儀(Imager of Sprites and Upper Atmospheric Lightning, ISUAL)專注於研究發生在對流層與電離層之間的高空短暫發光現象(Transient Luminous Events, TLEs)。ISUAL 於2004年7月至2016年6月任務期間全球性的觀測高空短暫發光現象,共紀錄了292,248筆強閃電事件,並以人工判讀辨識出48,537筆高空短暫發光事件。這些觀測資料深化了對於高空短暫發光現象的了解。然而,傳統人工判讀方法易因人為判斷標準不一致與判讀經驗的差異而產生誤差,尤其是多類型事件與弱發光事件。本研究運用深度學習技術,建立並訓練神經網路模型,系統性辨識出 66,586 筆事件,建立高空短暫發光現象事件資料庫用於後續的時空特徵研究。
本研究首度結合 ISUAL 高空短暫發光現象事件資料庫與地面閃電觀測網絡 (World Wide Lightning Location Network, WWLLN) 的強閃電分布,克服了ISUAL觀測所無法涵蓋的中高緯度與相鄰軌道間空窗區域,成功建立完整的全球高空短暫發光現象發生率地圖。校正後的全球高空短暫發光現象發生率達到每分鐘 47.08 次。其中各類型高空短暫發光現象的每分鐘發生率分別為:淘氣精靈(elves) 32.74、紅色精靈(sprites) 5.94、精靈暈盤(halos) 2.98、藍色噴流(blue jets) 5.40 與 巨大噴流(gigantic jets) 0.02。相較於過往的研究,本研究推估之高空短暫發光現象發生率大幅提升約一個數量級,這項新的統計結果將對於現有全球大氣電路模型與大氣化學模型中,高空短暫發光現象所反映之強閃電活動的貢獻與影響需重新評估。
此外,本研究依據柯本氣候分類 (Köppen classification) 系統性分析不同氣候環境下高空短暫發光現象發生率之變化。結果顯示,高空短暫發光現象在熱帶與溫帶地區的發生率較高,其中紅色精靈尤其集中於炎熱夏季型氣候區。為進一步探討外在因素的可能影響,本研究首次將完整的 11 年太陽活動週期與夜間高空短暫發光現象發生率進行相關性分析,結果顯示其相關性僅為弱相關(R ≤ 0.3),顯示氣象因素而非太陽活動更可能是主導高空短暫發光現象年際變化的主要驅動機制。
The Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite was designed to investigate Transient Luminous Events (TLEs) occurring between the troposphere and ionosphere. From July 2004 to June 2016, the ISUAL instrument recorded 292,248 intense lightning events, from which 48,537 TLEs were manually identified. These observations have substantially advanced our understanding of TLEs. However, manual classification is susceptible to biases arising from inconsistent judgment criteria and variations in observer experience, particularly for multi-type or dim events. In this study, deep learning techniques were employed to develop and train convolutional neural network models that systematically identified 66,586 TLEs events. The event list provides a more consistent and comprehensive foundation for subsequent analyses of the spatiotemporal characteristics of TLEs.
To overcome the observational gaps at mid- to high latitudes and the inter-track gaps between adjacent ISUAL ground tracks. This study first constructed a bias-corrected TLEs occurrence density map through the fusion of ISUAL TLEs observations and World Wide Lightning Location Network (WWLLN) intense lightning distributions. The global TLEs occurrence rate is 47.08 events per minute, with individual rates of elves (32.74), sprites (5.94), halos (2.98), blue jets (5.40), and gigantic jets (0.02). Compared with existing studies, the occurrence rate estimated in this work is approximately one order of magnitude higher, indicating that the current global atmospheric electric circuit and atmospheric chemistry models may need to re-evaluate the role of intense lightning activity reflected by TLEs observations.
Furthermore, TLEs occurrence rates were examined across different climate zones using the Köppen classification system. Higher rates were found in tropical and temperate climates, with sprites particularly frequent in hot summer regions. To further examine potential external drivers, this study for the first time analyzed a full 11-year solar cycle activity in relation to nighttime TLEs occurrence, revealing only a weak correlation (R ≤ 0.3) and favoring meteorological factors instead of solar activity as the primary drivers of TLEs variability.
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