| Project/Area Number |
17540407
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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 |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | Hirosaki University |
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Principal Investigator |
KODAMA Yasu-Masa Hirosaki University, Hirosaki University, Graduate School of Science and Technology, Associate Professor (30205421)
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| Co-Investigator(Kenkyū-buntansha) |
NINOMIYA Kozo Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Senior Research Scientist (60292950)
YOSHIKANE Takao Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Research Scientist (40392964)
SATO Naoki Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology, Postdoctoral Research Scientist (90392935)
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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 |
¥3,540,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥240,000)
Fiscal Year 2007: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | South Atlantic Convergence Zone (SACZ) / Subtropical Convergence Zone (STCZ) / Subtropical Frontal zone / Monsoon system / Baiu frontal zone / Atmospheric General Circulation Model / Regional Atmospheric Model / Topographic effect on precipitation / 亜熱帯域の降水帯 / SSTと降水活動 / 領域気候モデル |
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| Research Abstract |
South Atlantic convergence zone (SACZ) is significant precipitation zone developed in Austral summer between the Amazon basin and the South Atlantic passing through the southeastern part of Brazil, The first purpose of this study is to clarify the formation mechanisms of SACZ by statistical analysis of long-term observation data, and by numerical experiments using high-resolution (25 km) regional atmospheric model. The other purpose is to understand formation mechanisms of five subtropical convergence zones (STCZs) by comparing similarity and differences among the STCZs developed in different geographic conditions in the subtropics.
Statistical analysis using 27 years data indicates that SACZ is most intensified when SACZ is located over Brazilian Plateau (BP). When the SACZ is located BP, low-level cyclonic circulation appears over the southwestern part of BP and intensifies low-level convergence along the SACZ. Sensitivity experiments using the regional model are performed to clarify
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the mechanisms of the cyclonic circulation. The circulation is maintained not by dynamic process but by thermodynamic process of precipitation developed over BP. Complex terrain of BP is need to be represented by high-resolution model to simulate the precipitation over BP.
Five STCZs are compared with emphasizing their relationship to land-sea distributions. To reduce the influence of difference in observation density among the regions for STCZs, the output of long-term integration of CCSR/NIES/FRCGC atmospheric general circulation model is analyzed. SACZ and SICZ (South Indian convergence zone) over the western South Indian ocean are characterized with relatively large temperature gradient. This is because zonal extension of South American and African continents in the mid-latitudes is small and cool airmass over mid-latitude ocean influence these STCZs. BFZ (Baiu frontal zone) and NACZ (North American convergence zone) over the western North Atlantic are characterized with relatively weak temperature gradient. This is because zonal extension of Eurasian and North American continents is large and hot airmass developed over the continents influences these STCZs. SPCZ is located far away from continents and located in the latitudes lower than for the other STCZs. Temperature gradient in the subtropical portions is weak and characterized as a moisture frontal zone. Less
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