Observed Positive Vegetation-Rainfall Feedbacks in the Sahel Dominated by a Moisture Recycling Mechanism

TitleObserved Positive Vegetation-Rainfall Feedbacks in the Sahel Dominated by a Moisture Recycling Mechanism
Publication TypeJournal Article
Year of Publication2017
JournalNature Communications
Date Published11/2017
Abstract / Summary

Classic, model-based theory of land-atmosphere interactions across the Sahel promoted 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, although it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism, on the seasonal to interannual time scale. 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.

Journal: Nature Communications
Year of Publication: 2017
Date Published: 11/2017

Classic, model-based theory of land-atmosphere interactions across the Sahel promoted 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, although it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism, on the seasonal to interannual time scale. 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.

Citation:
Yu, Y, M Notaro, F Wang, J Mao, X Shi, and Y Wei.  2017.  "Observed Positive Vegetation-Rainfall Feedbacks in the Sahel Dominated by a Moisture Recycling Mechanism."  Nature Communications.