2003 Fiscal Year Final Research Report Summary
Elucidation of the formation of the Arctic Oscillation through the process of the Polar-night Jet Oscillation
| Project/Area Number |
14540412
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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 | Meteorological Research Institute, Japan Meteorological Agency (JMA) |
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Principal Investigator |
KURODA Yuhji Meteorological Research Institute, JMA, Climate Research Department, Senior Researcher, 気候研究部, 主任研究官 (80343888)
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| Co-Investigator(Kenkyū-buntansha) |
SHIBATA Kiyotaka Meteorological Research Institute, JMA, Atmospheric Environment and Applied Meteorology Research Department, Head, 環境・応用気象研究部, 室長 (50354494)
KODERA Kunihiko Meteorological Research Institute, JMA, Climate Research Department, Senior Researcher, 気候研究部, 主任研究官 (70343887)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Polar-night Jet Oscillation / Arctic Oscillation / Wave-mean flow interaction / Meridional circulation / North Atlantic Oscillation |
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| Research Abstract |
We have investigated the mechanism of how the Polar-night Jet Oscillation (PJO) induces to create the Arctic Oscillation (AO) through the analysis of the observational data and the simulation of the general circulation model. It was found that the Eulerian mean zonal-mean meridional circulation as well as the zonal-mean zonal wind was created by the wave forcing, and the AO signal at the surface was created through the meridional circulation. Results clarified in this study were summarized as follows :
1.There is a strong statistical dependence between the phase of the PJO which are defined by the temperature structures of the polar temperature, and the polarity of the AO. Namely when the PJO is in the phase of "annular stage", AO index at the surface significantly tend to have a polarity of positive or negative sign.2.Duration of the AO index strongly depends on the PJO. Especially, when the AO exists under the preferable condition of PJO as in 1., the lifetime of AO becomes significantly longer compared with that does not satisfy the condition.3.PJO is created through slowly evolving wave forcings. These wave forcings drive meridional circulation as well as force zonal wind. Interaction of the meridional circulation with the surface creates high (low) pressure anomaly at the area of descending (ascending) flow. In this way the AO signal was created by the wave-forced meridional circulation. Descending and ascending flow and the surface pressure change at the polar cap area is especially prominent. 4.For the formation of the PJO, thermal forcing from the wave of zonal wavenumber 1, which shows deep meridional dipole structure, is very important. The effect of the thermal forcing on the surface is nearly as important as that from the momentum forcing inside the troposphere. 5.The effect of wave forcing in the stratosphere to the surface AO is found to be very large, and it is as large as that in the troposphere.
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Research Products
(6 results)
