2022 Fiscal Year Final Research Report
Madden-Julian oscillation reproduced by an aqua-planet global cloud resolving model and its sensitivity to environmental conditions
| Project/Area Number |
19K03966
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 17020:Atmospheric and hydrospheric sciences-related
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| Research Institution | The University of Tokyo |
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Principal Investigator |
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | マッデン・ジュリアン振動 / 水惑星実験 / 全球雲解像モデル |
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| Outline of Final Research Achievements |
The Madden-Julian Oscillation (MJO), is a major fluctuation observed in the tropical atmosphere, which travels eastward on a time scale of several weeks to two months, strongly influencing the global weather and climate. The dependency of MJO to the environmental conditions is investigated in this study by an idealized "aqua-planet" version of the global cloud-resolving model NICAM, which is known for its good performance in reproducing the MJO eastward propagation. The simplification allows to extract the essential aspects of this phenomenon. Results are also compared to experiments conducted under more realistic settings, for interpretation. It was revealed that the east-west contrast in sea surface temperature is crucial for the eastward propagation of the MJO. Furthermore, it was found that the effect is enhanced by latent heat supply from the ocean associated with synoptic-scale atmospheric eddies occurring within the active convective envelope.
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| Free Research Field |
気象学/気候学
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| Academic Significance and Societal Importance of the Research Achievements |
MJOの東進に対して、どのような環境場と擾乱が影響しているかについての理解が進んだことにより、より正確な予報のためには数値予報モデルが、海面水温の東西差がよく表現できることと、海面からの潜熱供給を強化する渦擾乱を適切に表現できる解像度を有することが必要であることが明らかになった。MJOは数週間から2ヶ月程度の比較的長い時間スケールの現象である一方で、中緯度の多雨・小雨や熱波・寒波をもたらしたり台風発生の引き金となったりすることから、本研究による知見を参考にして今後数値予報モデルの改良が進むことにより、こうした現象の季節予測の精度向上に繋がることが期待できる。
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