Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism

Yan Yu, Michael Notaro, Fuyao Wang, Jiafu Mao, Xiaoying Shi, Yaxing Wei

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58 Scopus citations

Abstract

Classic, model-based theory of land-Atmosphere interactions across the Sahel promote positive vegetation-rainfall feedbacks dominated by surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback nor its underlying albedo mechanism has been convincingly demonstrated using observational data. Here, we present observational evidence for the region's proposed positive vegetation-rainfall feedback on the seasonal to interannual time scale, and find that it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism. Positive anomalies of remotely sensed vegetation greenness across the Sahel during the late and post-monsoon periods favor enhanced evapotranspiration, precipitable water, convective activity and rainfall, indicative of amplified moisture recycling. The identified modest low-level cooling and anomalous atmospheric subsidence in response to positive vegetation greenness anomalies are counter to the responses expected through the classic vegetation-Albedo feedback mechanism. The observational analysis further reveals enhanced dust emissions in response to diminished Sahel vegetation growth, potentially contributing to the positive vegetation-rainfall feedback.

Original languageEnglish
Article number1873
JournalNature Communications
Volume8
Issue number1
DOIs
StatePublished - Dec 1 2017

Funding

This work is funded by Department of Energy (DOE) Regional and Global Climate Modeling (RGCM) program and National Science Foundation (NSF) Climate and Large-Scale Dynamics (CLD) program. Computer resources are provided by DOE National Energy Research Scientific Computing Center (NERSC). The authors are thankful for helpful discussions with Drs. Zhengyu Liu, Yongkang Xue, Ankur Desai, Daniel Vimont, and Tristan L’Ecuyer.

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