2005 Fiscal Year Final Research Report Summary
The Role of Midlatitude and Subtropical Air-Sea Interactions in the Formation and Variability of the Atmospheric Circulation Systems
| Project/Area Number |
15340153
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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 | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NAKAMURA Hisashi The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (10251406)
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| Co-Investigator(Kenkyū-buntansha) |
TANIMOTO Youichi Hokkaido University, Graduate School of Environmental Science, Associate Professor, 大学院・地球環境研究院, 助教授 (00291568)
YAMANE Shozo Chiba Institute of Science, Faculty of Risk and Crisis Management, Lecturer, 危機管理学部, 講師 (10373466)
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| Project Period (FY) |
2003 – 2005
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| Keywords | subtropical anticyclones / stationary Rossby waves / storm tracks / extreme weather events Okhotsk High / Okhotsk High / land-sea thermal contrast / oceanic frontal zone / air-sea interaction |
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| Research Abstract |
・Unlike in other mid-latitude oceanic regions, anomalous surface heat flux in the North Pacific sub-arctic frontal zone is controlled by local sea-surface temperature (SST) anomalies associated with its inherent decadal variability. This oceanic thermal forcing accompanies meridional shift of the storm track. Our GPS-sonde observations have revealed that the frontal SST distribution accompanies spatial imhomogeneities in static stability and thereby downward momentum transport in the boundary layer, leading to positive correlation between SST and surface wind speed.
・In the Southern Hemisphere, the storm0track core is anchored throughout the year along the surface baroclinic zone associated with the major oceanic frontal zone in the Indian Ocean, where a polar-front jet (PFJ) with surface westerlies forms due to poleward eddy heat transport. We are the first to point out a possible dynamical association among a storm-track, PFJ and oceanic frontal zone. Over the South Pacific, the assoc
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iation is disturbed in winter when upper-level eddies are trapped into an intensified subtropical jet (STJ), below which surface baroclinicity. Our new concept can provide a plausible interpretation for the seasonal march in the North Pacific storm-track.
・We have revealed that the surface Okhotsk High forms in response to cold advection by anomalous low-level easterlies induced by an upper-level blocking high to its northwest, which amplifies due to local breaking of an Rossby wave-train propagating from northern Europe.
・As opposed to the previous understanding, we have revealed that the summertime subtropical anticyclones form in response to the profound thermal contrast between the cool eastern ocean and the warm, dry continent to its east.
・To the south of Australia, where a PFJ overlaps with the stratospheric polar-night jet, a vertical waveguide forms through which stationary Rossby wave-trains propagate from the lower stratosphere downward to generate localized anomalous circulation in the troposphere. Less
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[Journal Article] 北極振動2004
Author(s)
中村 尚, 山根 省三, 本田 明治, 大淵 済
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Journal Title
気象研究ノート(日本気象協会) 第206号
Pages: 145-158
Description
「研究成果報告書概要(和文)」より
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