Isual Publications 2014

Isual Publications 2014

  • id
  • date time
    2014-04-08 14:38:00
  • 2010
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  • 吳彥蓉(2010),‘聖嬰現象對高空短暫發光現象(淘氣精靈)與閃電活動之影響’,國立成功大學太空天文與電漿科學研究所(碩士論文)
  • 福衛二號高空大氣閃電影像儀(ISUAL)是全球第一個從太空中觀測高空短暫發光現象的衛星酬載。經過五年觀測已累積足夠的資料進行大氣放電現象的全球分佈時間序列之研究,並且第一次有機會以觀測資料探索大氣放電現象與聖嬰南方震盪之間的關係。為了確保ISUAL觀測資料未受儀器衰減影響,本論文分析了ISUAL光譜光度計的長期衰減變化,確認在資料時間範圍內的事件偵測率不受儀器調整與衰減兩項因素的影響。 

    以閃電影像偵測儀(LIS)所觀測的閃電、ISUAL所觀測的閃電與淘氣精靈(Elve)等三種不同閃電能量之大氣放電現象資料為樣本。透過建構不同季節、不同放電資料的事件密度以進行空間與時序分析。結果顯示自2004年6月起五年間全球ISUAL閃電與LIS閃電活動變化趨勢一致,且維持穩定均值,但是淘氣精靈發生率有逐年增加的趨勢。五年任務期間共經歷兩次反聖嬰期以及兩次聖嬰期,以標準化距平對三種大氣放電資料進行太平洋區域聖嬰南方震盪冷、暖時期趨勢探討,我們發現淘氣精靈的變化同時具有代表地球環境的太平洋馬蹄形區域以及閃電活動的大溪地附近區域之特徵。 

    分析大氣放電現象與聖嬰南方震盪指數的時間相關性找出之聖嬰南方震盪正負強反應區域,分別為換日線赤道區及大溪地區域。採用與南方震盪指數類似之定義,對不同放電現象之事件發生率進行計算,發現所得到的變化曲線與南方震盪指數、Niño 3.4指標皆有高度時間相關性。顯示閃電、淘氣精靈在太平洋區域的變化確實受到聖嬰南方震盪的影響,並且呈現顯著的關連性。

    Imager of Sprite and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite is the first space-borne scientific payload dedicated to the long-term survey of the transient luminous events (TLEs). To monitor the performance change of the ISUAL sensors, the instrumental degradation and the effective detection efficiency is carefully investigated by the routine calibration observations. The chronic variation of TLE event rates show no notable trend between the annual cycles; this result implies that the detection efficiency of ISUAL has maintained at a constant level in the first 5 years of operation and no correction to the current statistics is necessary. 

    We analyze 3 datasets of atmospheric discharge observations from the space, ISUAL-recorded elve, lightning, and LIS-recorded lightning, covering the average energies from high to low respectively. The ISUAL lightning and the LIS lightning rates show similar trend and remain nearly constant from June 2004 to the present, while the seasonal rates of elve increase gradually. Two El Niño events and two La Niña events have experienced in the past 5 years. A standardized anomaly analysis is adapted to identify the elves and lightning variability in the warm and cold phases of ENSO, which is characterized by the South Oscillation Index. The anomaly elve distributions during these episodes are consistent with the Pacific horseshoe pattern and the ENSO lightning characteristics in the Tahiti region. 

    The correlation between the atmospheric discharges and the major indices that scientist commonly use to identify ENSO, such as Southern Oscillation Index and Niño 3.4 Oceanic Niño Index, is discussed. The equatorial dateline and the Tahiti regions are chosen as a comparative areas for the elve and lightning as they response to the ENSO episodes. The tight correlation between the atmospheric discharges and ENSO interannual variability provides the concrete evidence that the electricity activity at upper atmosphere can be directly affected by the variation of the ocean and atmosphere conditions.  

Tuesday the 24th. ISUAL. All rights reserved.