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Impact of the sea surface temperature in the north-eastern tropical Atlantic on precipitation over Senegal
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  • Mamadou Thiam,
  • Ludivine Oruba,
  • Gaelle De Coetlogon,
  • Malick Wade,
  • Bouya Diop,
  • Abdou Karim Farota
Mamadou Thiam
Université Gaston Berger

Corresponding Author:[email protected]

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Ludivine Oruba
Sorbonne Universite
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Gaelle De Coetlogon
Sorbonne Université
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Malick Wade
Université Gaston Berger
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Bouya Diop
Université Gaston Berger
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Abdou Karim Farota
Université Gaston Berger
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Abstract

This study examines 40 years of monthly precipitation data in Senegal (1979-2018) using CRU observations and ERA5 reanalyses, aiming to understand the influence of oceanic and atmospheric factors on Senegal’s precipitation in July, August and September (JAS). Comparing Senegal’s precipitation variability with the broader Sahel region, it emerges that Senegal’s precipitation is more closely associated with the Northeastern Tropical Atlantic (NETA) Sea Surface Temperature (SST). The increased Senegal’s precipitation is linked to the northward shift of the InterTropical Convergence Zone (ITCZ), consistent with numerous previous studies. Over the continent, this shift corresponds to a northward shift of the African Easterly Jet (AEJ) and, consequently, the Mesoscale Convective Systems responsible for most precipitation. It seems primarily driven by the northward shift of the Heat Low.Over the ocean west of Senegal, there is a comparable shift of the AEJ, accompanied by increased low-level moisture transport convergence within the West African Westerly Jet (WAWJ). This phenomenon is triggered by a negative pressure anomaly in the NETA, located above a positive SST anomaly: we suggest that the latter is the origin of the former, forming a feedback mechanism that potentially significantly influences Senegal’s precipitation. The mechanism involves a geostrophic adjustment of the WAWJ to the southern gradients of the SST anomaly. To validate the NETA SST feedback’s role in Senegal’s precipitation, further investigations using daily data or regional atmospheric models are recommended. The findings hold potential for enhancing seasonal forecasting capabilities.
01 Dec 2023Submitted to ESS Open Archive
03 Dec 2023Published in ESS Open Archive