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Frequent but Predictable Droughts in East Africa Driven by A Walker Circulation Intensification
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  • Chris Funk,
  • Andreas H. Fink,
  • Laura Harrison,
  • Zewdu Segele,
  • Hussen Seid Endris,
  • Gideon Galu,
  • Diriba Korecha,
  • Sharon E. Nicholson
Chris Funk
University of California, Santa Barbara

Corresponding Author:chris@geog.ucsb.edu

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Andreas H. Fink
Karlsruhe Institute of Technology
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Laura Harrison
University of California, Santa Barbara
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Zewdu Segele
IGAD Climate Prediction and Applications Centre [ICPAC]
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Hussen Seid Endris
IGAD Climate Prediction and Applications Center
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Gideon Galu
United States Geological Survey
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Diriba Korecha
Famine Early Warning Systems Network
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Sharon E. Nicholson
Florida State University
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The decline of the eastern East African (EA) March-April-May (MAM) rains poses a life-threatening “enigma,” an enigma linked to sequential droughts in the most food-insecure region of the world. The MAM 2022 drought was the driest on record, preceded by three poor rainy seasons, and followed by widespread starvation. Connecting these droughts is an interaction between La Niña and climate change, an interaction that provides exciting opportunities for long-lead prediction and proactive disaster risk management. Using observations, reanalyses, and climate change simulations, we show here, for the first time, that post-1997 OND La Niña events are robust precursors of: (1) strong MAM “Western V Gradients” in the Pacific, which help produce (2) large increases in moisture convergence and atmospheric heating near Indonesia, which appear associated with (3) regional shifts in moisture transports and vertical velocities, which (4) help explain more frequent dry EA rainy seasons. Understanding this causal chain will help make long-lead forecasts more actionable. Increased Warm Pool atmospheric heating and moisture convergence sets the stage for dangerous sequential droughts in EA. At 20-year time scales, we show that these Warm Pool heating increases are attributable to observed Western V warming, which is, in turn, largely attributable to climate change. As energy builds up in the oceans and atmosphere, we see stronger convergence patterns, which offer opportunities for prediction. Hence, linking EA drying to a stronger Walker Circulation can help explain the “enigma” while underscoring the predictable risks associated with recent La Niña events.
31 Jan 2023Submitted to ESS Open Archive
09 Feb 2023Published in ESS Open Archive