サヘルの降雨の海洋的な強制は,年間から十年間までの時間スケールで発生します

A Giannini¹, R Saravanan, P Chang

¹National Center for Atmospheric Research, Boulder, CO 80305, USA. alesall@iri.columbia.edu

Science (New York, N.Y.)

|October 11, 2003

まとめ

サヘルの降雨の変動は,海洋の温度に対応するアフリカの夏季季風によって引き起こされます. 暖かい水は海洋のコンベクションを強め,モンスーンを弱め,地域全体で干ばつを引き起こします.

科学分野:

気候科学気候科学
大気科学大気科学
気象学気象学気象学

背景:

サヘル地域は,数百万人に影響を及ぼす,著しい降雨変動を経験しています.
サヘルの干ばつの原因を理解することは,地域の安定と食糧安全保障にとって極めて重要です.

研究の目的:

海面温度とサヘルの降雨変動の関係について調査する.
サヘルの最近の乾燥傾向を促すメカニズムを特定する.

主な方法:

NASAゴダード宇宙飛行センターの大気一般循環モデル (NSIPP1) との統合を活用した.
1930年から2000年までの観測された海面温度データを用いてモデルを強制した.
海洋力や陸地-大気相互作用に対するモデルの反応を分析した.

主要な成果:

サヘルの降雨の変動は,主に,アフリカの夏季モンスーンの海洋的な強制への反応である.
アフリカ周辺の低緯度の暖かい水域は,最近のサヘルの乾燥傾向と関連していた.
暖かい海洋は,沖合の深いコンベクションを促進し,大陸のモンスーンの収束を弱め,干ばつにつながります.

結論:

海洋的強制,特に海面温度は,アフリカの夏季季風とサヘルの降雨を調節する上で重要な役割を果たしています.
陸地と大気の相互作用は,海洋の変化に対するモンスーンの反応を強める.
発見は,サヘル地域の最近の干ばつを特定の海洋条件に起因し,予測と緩和のための洞察を提供している.

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