TITLE:
Hydroclimatic Analysis of the Unusual Wet Spell Observed in Senegal in July 2022
AUTHORS:
Abdou Lahat Dieng, Dahirou Wane, Coumba Niang, Dame Gueye, Saïdou Moustapha Sall, Aida Diongue, Amadou Thierno Gaye
KEYWORDS:
Wet Spell, African Easterly Wave, Sea Surface Temperature, SST Index, MJO, Senegalese Rainfall
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.16 No.3,
July
24,
2026
ABSTRACT: In July 2022, Senegal experienced an exceptional wet spell characterized by widespread flooding and anomalously high rainfall intensity. This study investigates the multi-scale hydroclimatic mechanisms underlying this event, focusing on the combined roles of sea surface temperature (SST) anomalies, African Easterly Waves (AEWs), and intraseasonal variability associated with the Madden-Julian Oscillation (MJO). We combine satellite-based precipitation products (IMERG, CHIRPS, and TAMSAT), ERA5 reanalysis fields, and daily SST data (OISST v2) to diagnose the large-scale and mesoscale processes involved. AEWs and mesoscale convective systems (MCSs) are objectively tracked to quantify their contribution to rainfall variability. The results show that the event coincided with a pronounced tropical Atlantic SST dipole, characterized by anomalous warming in the North Tropical Atlantic and cooling along the equatorial Atlantic. This configuration enhanced the meridional SST gradient, strengthened the low-level monsoon flow, and increased moisture availability over West Africa. During the same period, total column water vapor exceeded 59 mm over Senegal, while a sequence of long-lived and coherently propagating AEWs was observed. Moreover, this event occurred during an active MJO phase (phases 8 - 1), which is known to favor enhanced convection over West Africa. The MJO likely acted as an intraseasonal modulator, reinforcing large-scale ascent and moisture convergence, thereby amplifying convection triggered by AEWs. The extreme rainfall arose from a compound mechanism involving persistent AEW activity, a moisture-rich background state, and favorable intraseasonal conditions linked to the MJO. These results underscore the role of multi-scale interactions in shaping extreme rainfall over west Africa and offer valuable insights for improving subseasonal forecasting and early warning systems.