| Project/Area Number |
18K13625
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 17030:Human geosciences-related
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| Research Institution | Waseda University |
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Principal Investigator |
Nagai Hiroto 早稲田大学, 教育・総合科学学術院, 講師(任期付) (50771474)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2019: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Keywords | 氷河湖 / 氷河湖決壊洪水 / ブータンヒマラヤ / 合成開口レーダー / リモート・センシング / GLOF / SAR / 自動抽出 / GIS / 合成開口レーダ / ヒマラヤ |
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| Outline of Final Research Achievements |
An automatic glacier lake extraction method was established using synthetic aperture radars (SARs), and the time series of glacial-lake area were analyzed using this method. L-/C-band SARs could be appropriate, whereas the area was underestimated due to the surface waves in high-resolution modes (~3 m), .
As a result of temporal analysis using C-band SAR observed every 12 days, many glacier lakes tend to expand/shrink in summer/winter. It is possible to develop and update a glacial lake database with weekly intervals. Significant technological development has been achieved for understanding glacier lake changes.
We examined the relationship between the temporal changes of glacier lakes and meteorological conditions, where no significant relationship were found. In the years of flood, common meteorological characteristics were not found. To examine the flood causes, a more local meteorological and topographical analysis would be needed.
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| Academic Significance and Societal Importance of the Research Achievements |
広域に分布する氷河湖の面積を高頻度(~12日)に把握する手法が概ね確立された。従来は一度きりの氷河湖マッピングがほとんどであったが、合成開口レーダー衛星から自動的に何度も氷河湖マップを更新できるようになり「動的なデータベース」へのアップデートが達成されると期待される。
またこの手法を用いて、多くの氷河湖が年周期の拡大縮小を繰り返していることが明らかになった。これまでは温暖化によって氷河が融けて氷河湖が拡大し、洪水に至ることが危惧されてきたが、氷河湖の面積には季節変動も含まれるため、観測時期を揃えた氷河湖面積解析が必要であるという示唆が得られた。
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