| Project/Area Number |
12554015
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
NARUSE Renji Hokkaido University, Institute of Low Temperature Science, Associate Professor, 低温科学研究所, 助教授 (10002099)
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| Co-Investigator(Kenkyū-buntansha) |
INAGAKI Masaharu Walnut Ltd., Technical manager, 技術部長
MAENO Hideo Communication Research Laboratory, Researcher, 地球環境計測部, 研究官
TAKEI Iwao Hokuriku University, Faculty of Pharmaceutical Sciences, Lecturer, 薬学部, 講師 (70247477)
FUJITA Shuji Hokkaido University, Faculty of Engineering, Instructor, 大学院・工学研究科, 助手 (30250476)
SHIRAIWA Takayuki Hokkaido University, Institute of Low Temperature Science, Instructor, 低温科学研究所, 助手 (90235739)
松岡 健一 総合地球環境学研究所, 日本学術振興会特別研究員
曽根 敏雄 北海道大学, 低温科学研究所, 助手 (10222077)
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| Project Period (FY) |
2000 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥10,200,000 (Direct Cost: ¥10,200,000)
Fiscal Year 2002: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2001: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2000: ¥6,700,000 (Direct Cost: ¥6,700,000)
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| Keywords | Ice radar / Glacier / Ground-penetrating radar / Impulse radar / Snow cover / Snow structure / Snow water equivalent / Ice thickness / インパルスレーダ / アサバスカ氷河 / 山岳氷河 / 内部反射層 / 氷厚測定 / 電波伝搬 / 低周波レーダ / 高周波レーダ / 積雪層構造 |
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| Research Abstract |
We have developed a novel ice-penetrating radar system that can be carried on a backpack. Including batteries for a three-hour continuous measurement, the total weight is 13 kg. In addition, it operates reliably down to -25°C, has a low power consumption of 24 W, and is semi-waterproof. The system has a built-in-one controller with a high-brightness display for reading data quickly, a receiver with 12-bit digitizing, and a 1-kV pulse transmitter with time variance of the pulse amplitude of less than 0.2%. The optical communications between components provides low-noise data acquisition and allows synchronizing of the pulse transmission with sampling. Measurements with this system successfully illustrate 300-m deep bed topography of Athabasca Glacier, Canada, in summers 2001 and 2002.
To complement a technique to detect internal structures of seasonal snow-covers and glacier firn with ground-penetrating radar (GPR), we carried out calibration experiments and an observation of winter snow-cover (5.7 m thick dry snow with numerous ice layers) with an 800-MHz GPR. In particular, we aimed to discriminate periodic noise from radar echoes, which is inherent in GPR, and to obtain a relationship between the observed reflection strength and the magnitude of density contrasts. Experiments were made in the open space to evaluate noise levels and receiver characteristics of this system. Based on these, we removed noise from radar echoes in the snow-cover observation. We recognized numerous marked echoes in a noise-free radargram. Depths of these echoes coincided roughly with those of large density contrasts observed in the snow-pit. Thus, we argue that the echoes correspond to thin ice layers. Furthermore, the minimum density contrasts to be detected by this GPR are found to vary from about 100 to 250 kg m"3 with the depth from 1 to 6 m in the seasonal snow-cover.
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