地元の海面温度に対する熱帯降雨の高感度
Peter Good1, Robin Chadwick2,3, Christopher E Holloway4
1MetOffice Hadley Centre, Exeter, UK. peter.good@metoffice.gov.uk.
Nature
|October 27, 2020
まとめ
熱帯の海温度は地球全体の天候に強い影響を与えている. 気候モデルと予測の改善に不可欠な発見である. 気候モデルと予測の改善に不可欠な発見である.
科学分野:
- 気候科学
- 大気科学
- 海洋学
背景:
- 熱帯海面の温度は,降水と大気循環のプロセスによる地球的な天気と気候の主要な原動力です.
- 既存の気候モデルは,不正確な熱帯雨帯や弱いエルニニョ南方振動 (ENSO) 反応などのバイアスを示しており,海洋と大気の相互作用を理解する際のギャップを示しています.
- 浅い大気循環が降水に影響を与える役割と,深い循環との相互作用は不明であり,気候モデリングをさらに複雑にします.
研究 の 目的:
- 観測データを用いて,季節的な熱帯降雨の局所海面温度に対する感度を定量化する.
- 観測による降水感度の推定値と気候モデルによる推定値を比較する.
- 浅い循環とモデルバイアスの関連性を特定し,将来の気候予測を改善する.
主な方法:
- 複数の独立した観測データセット,物理的制約,気候モデルデータの分析.
- 海面温度の関数である飽和特異湿度の単位変化による降水変化の見積もり.
- 観測の推定値に対する気候モデルの性能の評価と,浅いコンベクションに関連するバイアスの評価.
主要な成果:
- 観測された季節的な熱帯降雨は,局所海面温度に対する飽和特異湿度変化の1グラムあたり80%の高い感度を示している.
- この感度値は,研究された気候モデルの大部分 (47本中43本) よりも著しく高い.
- より現実的な降水感度 (80%に近い) を示すモデルは,様々なメトリック,特に浅いコンベクションに関連したバイアスの減少を示しています.
結論:
- 浅い循環によって引き起こされる熱帯降雨の海面温度に対する高い感受性は,正確な気候モデリングに不可欠です.
- 気候モデルにおける浅いコンベクションと降水感度の表現を改善することは,バイアスを軽減し,季節的予測と多十年的な気候予測の信頼性を高めるために不可欠です.
- この研究は,海洋と大気の結合とその地球温暖化への影響の理解を深めるための将来の研究に明確な焦点を提供します.
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