| イベント名 |
第8回 地球惑星科学教室談話会 Stratosphere–Troposphere Coupling: Mechanisms Underlying the QBO–MJO Connection |
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| イベント種類 | セミナー |
| 講演者(講師) | Seok-Woo Son (School of Earth and Environmental Sciences, Seoul National University) |
| イベント詳細 | The Quasi-Biennial Oscillation (QBO) and the Madden–Julian Oscillation (MJO) are strongly coupled during the boreal winter. Observational evidence shows that the MJO is approximately 40% stronger and persists about 10 days longer during the QBO easterly phase (EQBO) than during its westerly phase (WQBO). Despite the robustness of these observations, numerical models fail to reproduce this QBO–MJO connection, and the underlying physical mechanisms remain a subject of active debate. In this presentation, I explore two leading hypotheses explaining the QBO–MJO connection. The first focuses on the Kelvin-wave-like cold anomalies in the upper troposphere and lower stratosphere (UTLS) that weaken local static stability. Idealized model experiments indicate that these MJO-induced cold anomalies are intensified during EQBO, as QBO zonal winds modulate the vertical propagation of Kelvin waves in the UTLS. The second hypothesis concerns longwave cloud–radiative feedback within the MJO envelope. Analysis of satellite datasets reveals that cloud-top pressure and brightness temperature of deep convection are systematically lower during EQBO. These deeper clouds are more effective at trapping outgoing longwave radiation, thereby enhancing the cloud–radiative feedback that sustains and strengthens the MJO. Finally, the current challenges and limitations in modeling the QBO–MJO connection are briefly discussed. |
| 対象 | 教職員向け 在学生向け |
| 使用言語 | 英語 |
| キーワード | |
| 開催期間 | 2026年2月4日 16:40 〜 17:40 |
| 会場 |
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| 定員 | なし |
| 申込み方法 | 事前申込み不要 |
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