Increasing Influence of Indian Ocean Dipole on Precipitation Over Central Equatorial Africa

Using observational rainfall datasets, we identify a positive correlation between precipitation over Central Equatorial Africa (CEA) and the Indian Ocean Dipole (IOD) during September-December (SOND) for the period 1981-2019. Rainfall amount significantly increases during positive IOD events. The enhancement in precipitation is primarily attributed to increased rainfall frequency and reaches the maximum in October. IOD impacts rainfall via modifying the Walker circulation over the tropical Indian Ocean and moisture in the middle troposphere over CEA. The Madden-Julian Oscillation (MJO) activity covaries with IOD to modulate the African Easterly Jet, which is critical to convection development over CEA. SOND rainfall has increased for the last two decades, which is concurrent with increases in both the IOD index and the correlation between IOD and rainfall. The IOD-congruent rainfall changes potentially account for much of rainfall trends in southern and eastern CEA.

Automated summary

Using observational rainfall datasets, a positive correlation was found between precipitation over CEA and IOD during September-December for the period 1981-2019. Rainfall increases significantly during positive IOD events, primarily due to an increase in rainfall frequency reaching its peak in October. IOD impacts rainfall by modifying Walker circulation over the tropical Indian Ocean and moisture in the middle troposphere over CEA, with MJO activity covarying with IOD to modulate the African Easterly Jet critical for convection development over CEA.