2002 Fiscal Year Final Research Report Summary
A baroclinic atmosphere without baroclinic waves -A new approach to low-frequency variability
| Project/Area Number |
12640422
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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 | Kyushu University |
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Principal Investigator |
ITOH Hisanori Kyushu University, Faculty of Sciences, Prof., 理学研究院, 教授 (80112100)
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| Project Period (FY) |
2000 – 2002
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| Keywords | low-frequency variability / baroclinic wave / blocking / teleconnection / time filter / atmospheric general circulation model |
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| Research Abstract |
The most difficult thing in understanding the mechanism of low-frequency variability (LFV) is the interaction with high-frequency variability (HFV). Therefore, if we can obtain "pure" LFV without interacting with HFV, it greatly helps understand the mechanism. Then, we first construct the atmospheric general circulation model to generate "pure" LFV, using a time filter method.
The output by this model is compared with that of the control experiment which is carried out without using a time filter method. The standard deviation of the "pure" LFV shows that the values of the maxima in both the Pacific and the Atlantic are weaker than those in the control experiment. Also, the relationship between the LFV in the Pacific and that in the Atlantic is examined, indicating that the "pure" LFV in the Pacific and that in the Atlantic are coherent. This is contrast to the fact that they are not coherent in the control experiment.
We also made a data analysis about the interaction between LFV and HFV. First of all, we show that the Arctic Oscillation is apparent, which is falsely extracted from two independent oscillations, the NAG (North Atlantic Oscillation) and the PNA (Pacific/North American Oscillation), due to a characteristic of the analysis method. Therefore, we treat the NAO and PNA as basic LFVs. As a result, it is found that HFV effectively interact with the NAO and PNA, maintaining these LFVs.
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