| Project/Area Number |
17204041
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Nagoya University |
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Principal Investigator |
NAKAMURA Kenji Nagoya University, Hydrospheric Atmospheric Research Center, Professor (20262917)
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| Co-Investigator(Kenkyū-buntansha) |
UYEDA Hiroshi Nagoya University, Hydrospheric Atmospheric Research Center, Professor (80184935)
HIYAMA Tetsuya Naeova University, Hydrospheric Atmospheric Research Center, Associate Professor (30283451)
ABE Osamu Nagoya University, Graduate School of Environmental Studies, Assistant Professor (00293720)
SHINODA Taro Naeova University, Hydrospheric Atmospheric Research Center, Assistant Professor (50335022)
HIGUCHI Atsushi Chiba University, Center for Environmental Remote Sensing, Associate Professor (90324384)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥30,810,000 (Direct Cost: ¥23,700,000、Indirect Cost: ¥7,110,000)
Fiscal Year 2007: ¥9,100,000 (Direct Cost: ¥7,000,000、Indirect Cost: ¥2,100,000)
Fiscal Year 2006: ¥9,880,000 (Direct Cost: ¥7,600,000、Indirect Cost: ¥2,280,000)
Fiscal Year 2005: ¥11,830,000 (Direct Cost: ¥9,100,000、Indirect Cost: ¥2,730,000)
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| Keywords | Meso-Scale Precipitation System / Isotopic Composition of Precipitation / Precipitation System / Water Vapor Amount / Drop size distribution / 降水同位体比 / 層状性降水 / 対流性降水 / 粒径別同位体交換モデル / CIP法 / 釜石鉱山立坑 / 水滴落下実験 / 酸素安定同位体比 / 水素安定同位体比 / 雨滴粒径分離採取 / 三フッ化コバルト / 微量水同位体比分析 |
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| Research Abstract |
Analyses of oxygen isotopic composition of precipitation with several minutes intervals and meteorological observation by a polarimetric Doppler radar and GPS sondes were conducted during rainy season in 2004 at Okinawa. Large isotopic variation observed in event-to-event precipitation, in spite of the same vapor origins, implied that precipitation type (convective or stratiform) significantly affected isotopic values. Moreover, isotopic variation during convective precipitation was strongly affected by dryness in the middle troposphere before development of the convective system.
Based on the intra-event analyses of isotopic variation, it was found that the development stage of convective systems strongly related to isotopic values. Isotopic values showed gradual decreasing trends in the developing stage, whereas they showed V-shape patterns in the dissipating stage of convective systems. These V-shape patterns could be caused by significant evaporation of falling raindrops.
For quantit
… More
ative evaluation of isotopic change during raindrop falling, "isotopic exchange model of between raindrop and vapor for each size" was developed. As a result of sensitivity experiment, isotopic shifts were larger in smaller raindrops or at lower relative humidity. It could be demonstrated that relative humidity below cloud base was a significant controlling factor for the isotopic values of bulk(weighted mean)precipitation.
Drop-size distribution of isotopic values in precipitation, which was expected from the model simulation, was observed by a raindrop collection method using liquid nitrogen and the isotope analysis for micro-liter of water samples. All observed results of three rainfall events at Nagoya in 2007 showed that higher hydrogen and oxygen isotopic values were found in smaller raindrops, which were consistent with the model calculation.
Our results clearly indicate that the difference of cloud types and the evaporation effect during falling raindrops should be taken into account for the variation of isotopic composition of precipitation, not only the difference of vapor sources as discussed previously. Less
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