Similarities and Differences in Convectively Coupled Equatorial Waves and MJO(Fostering Joint International Research)

2019 Fiscal Year Final Research Report

• Project/Area Number: 16KK0095
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: University of Toyama
• Principal Investigator: Yasunaga Kazuaki 富山大学, 学術研究部都市デザイン学系, 教授 (50421889)
• Project Period (FY): 2017 – 2019
• Keywords: 赤道波 / MJO / 対流

Outline of Final Research Achievements

The present investigation examined the budget of column-integrated moist static energy in wavenumber-frequency transforms of longitude-time sections over the tropical belt, making use of cross-spectra with satellite-derived precipitation, and clarified similarities and differences in the moisture evolution and propagation mechanisms associated with convectively-coupled equatorial waves (CCEWs), Madden-Julian oscillation (MJO), and tropical depression-type disturbances (TDs). 2 leading modes of the vertical wind profiles were identified, and phase relationships between the 2 modes were also examined to elucidate the different vertical (tilting) structures among the CCEWs, MJO and TDs. In addition, new mechanisms of the moisture accumulation over the eastern Indian Ocean were proposed, comparing probability functions of each term in the moisture budget equation.

Free Research Field

熱帯気象

Academic Significance and Societal Importance of the Research Achievements

赤道域では，日本の位置する中緯度と違って温帯の低気圧は存在せず，雲・降水の発達は赤道波やMJOとよばれる擾乱よって大きく影響を受けている．しかし，「どのように影響を受けているか」については分かっていない．大枠での理論体系がほぼ確立している中緯度に比べて，熱帯気象学の未成熟さを表しており，本研究成果は熱帯気象学の確立のための大きな意義を持つ．また天気予報のベースとなる数値予報で用いられる数値モデルにおいて，熱帯の降水活動の再現性が低く，１週間以上という中・長期の天気予報の精度向上の足かせとなっている．このことから本研究成果は，社会的にも重要な役割を果たしている天気予報の精度向上にも貢献し得る．