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Title: Rainfall trends in the African Sahel: Characteristics, processes, and causes

Journal Article · · Wiley Interdisciplinary Reviews. Climate Change
DOI: https://doi.org/10.1002/wcc.591 · OSTI ID:1670846

Sahel rainfall is dynamically linked to the global Hadley cell and to the regional monsoon circulation. It is therefore susceptible to forcings from remote oceans and regional land alike. Warming of the oceans enhances the stability of the tropical atmosphere and weakens deep ascent in the Hadley circulation. Warming of the Sahara and of the nearby oceans changes the structure and position of the regional shallow circulation and allows more of the intense convective systems that determine seasonal rain accumulation. These processes can explain the observed interannual to multidecadal variability. Sea surface temperature anomalies were the dominant forcing of the drought of the 1970s and 1980s. In most recent decades, seasonal rainfall amounts have partially recovered, but rainy season characteristics have changed: rainfall is more intense and intermittent and wetting is concentrated in the late rainy season and away from the west coast. Similar subseasonal and subregional differences in rainfall trends characterize the simulated response to increased greenhouse gases, suggesting an anthropogenic influence. While uncertainty in future projections remains, confidence in them is encouraged by the recognition that seasonal mean rainfall depends on large-scale drivers of atmospheric circulations that are well resolved by current climate models. Nevertheless, observational and modeling efforts are needed to provide more refined projections of rainfall changes, expanding beyond total accumulation to metrics of intraseasonal characteristics and risk of extreme events, and coordination between climate scientists and stakeholders is needed to generate relevant information that is useful even under deep uncertainty.

Research Organization:
Columbia Univ., New York, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC); National Aeronautics and Space Administration (NASA); USDOE
Grant/Contract Number:
SC0014423; 1612904; 1565522; NNX16AN29G; DE‐SC0014423
OSTI ID:
1670846
Alternate ID(s):
OSTI ID: 1612182; OSTI ID: 1670848
Journal Information:
Wiley Interdisciplinary Reviews. Climate Change, Vol. 10, Issue 4; ISSN 1757-7780
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English

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