Impact of the sea surface temperature in the north-eastern tropical
Atlantic on precipitation over Senegal
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.