1999 Fiscal Year Final Research Report Summary
Development for measurement of physical characteristics of falling snowflake and its application to radio wave attenuation
| Project/Area Number |
09555124
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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 |
計測・制御工学
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| Research Institution | Kanazawa University |
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Principal Investigator |
MURAMOTO Ken-ichiro Faculty of Engineering, Kanazawa University, Professor, 工学部, 教授 (70042835)
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| Co-Investigator(Kenkyū-buntansha) |
SHIINA Toru Toyama National College of Technology, Associate Professor, 助教授 (80196344)
HARIMAYA Toshio Graduate School of Science Hokkaido University, Professor, 大学院・理学研究科, 教授 (90001859)
NAGANO Isamu Faculty of Engineering, Kanazawa University, Professor, 工学部, 教授 (50019775)
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| Project Period (FY) |
1997 – 1999
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| Keywords | image processing / snowflake / falling pattern / size distribution / snowfall rate / radar reflectivity factor / radio wave attenuation |
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| Research Abstract |
It is thought that snowflakes grow by the collision and adhesion of snowflake crystals during their fall. This growing process is effected by shape and falling motion of snowflake. It is not only important in consideration relating to the cloud physics, but also for various engineering applications such as remote sensing and telecommunications and lately in the field of global climate monitoring. Precipitation phenomena play an important part in fields related to radio wave attenuation and propagation. In the study of precipitation, one of the main instrument used is the radar. Radar measurements of precipitation are based on the relation between the radar reflectivity factor Z and precipitation rate R. In order to determine the Z-R relationship for snowfall, Z and R have to be measured independently with high accuracy at short time intervals. However, few systems have been developed for measurement of snowfall rate with high degree of accuracy and temporal resolution.
In order to measure the physical parameter of snowflakes, natural falling snowflakes were photographed by TV cameras. The diameter, velocity and density of each snow particle were computed from these images. Snowfall rates calculated from image data are computed with values directly obtained using an electronic balance. During this observation, the received power was measured using a small X-band Doppler radar. The relationship between X-band wave attenuation and snowfall rate was investigated and compared to the physical characteristics of snow particles. It was suggested that the power spectrum was related with the density of snow particles.
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