| Project/Area Number |
08650515
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計測・制御工学
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| Research Institution | Toyo University |
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Principal Investigator |
ITO Shigeo Toyo University, Faculty of Engineering, Professor, 工学部, 教授 (30223150)
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| Co-Investigator(Kenkyū-buntansha) |
OGUCHI Tomohiro Kanto Gakuin University, Faculty of Engineering, Professor, 工学部, 教授 (20233489)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1996: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | RANDOM MEDIA / RADAR / ELECTROMAGNETIC SCATTERING / RAIN / MILLIMETER WAVES / MULTIPLE SCATTERING / PROPAGATION / 降雨 / 散乱 |
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| Research Abstract |
For millimeter wave regions, the effects of multiple scattering in rain on radar signals may not be ignored for higher frequencies or higher rainfall rates. The theoretical estimation of rainfall rate has been based on the conventional polarimetric radar equation, which only takes account of the first-order scattering contribution. However, air-borne radar measurements of rain have shown very high depolarization ratios at 34.5GHz and suggested that the multiple scattering is included. The purpose of this paper is to clarify the effects of multiple scattering on radar signals in the time domain and to apply to the development of the radar systems with higher precision. To examine multiple scattering effects, the second-order solution of the radiative transfer equation was derived for the linearly polarized incident waves. Both of co-polarized and cross-polarized intensities were calculated. The theoretical results indicate a slower decrease in the co-polarized intensity against the range from the radar and a rapid increase in the linear depolarization ratio (LDR) near the rear edge of the rain layr. The laboratory measurements under controlled scattering parameters were made for simulated rain of randomly distributed spherical scatterers at 16.5GHz and 30GHz. The measured LDR is very large and is in remarkably good agreement with theoretical calculations. Therefore, the conventional radar equation may overestimate the rainfall rates in view of the present analysis. The simultaneous observation of co-and corss-polarized intensity would lead to estimate the higher precise rainfall rate and would need to analyze the fine structure of rain. We will further examine an alternative approximate solution of the radiative transfer equation and consider to treat the case of the nonspherical raindrops. The similar experiment should be done for various kind of size parameters of the raindrops.
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