Original Contribution to Understanding the Teleconnection Between Indian Ocean Dipole Events and North East Nigerian Rainfall Variability

The Indian Ocean Dipole (IOD), characterized by differential warming between the western and eastern tropical Indian Ocean, has been documented as a significant modulator of East African rainfall but its teleconnection to West African and specifically North East Nigerian rainfall has received minimal rigorous investigation. This study presents an original empirical and theoretical contribution to understanding the IOD-North East Nigeria rainfall teleconnection using observational analysis, reanalysis diagnostics, and atmospheric model sensitivity experiments. Monthly rainfall records from 14 NiMet stations in Borno, Yobe, Adamawa, Gombe, and Bauchi states for the period 1979 to 2022 were correlated with the Dipole Mode Index (DMI) using partial correlation analysis controlling for simultaneous ENSO effects. Composite circulation anomaly analysis using ERA5 for strong positive and negative IOD events revealed the atmospheric bridge mechanism mediating the teleconnection. Results demonstrate a statistically significant positive correlation between positive IOD events and above-normal July to September rainfall in Adamawa and Borno states (r = 0.48, p less than 0.01) that is independent of ENSO at seasonal timescales. Reanalysis diagnostics confirm that the mechanism operates through IOD-driven modifications of the Somali jet and Walker circulation, modulating moisture transport into the Lake Chad basin. WRF boundary condition perturbation experiments reproducing IOD-like SST anomalies confirm the rainfall response through mesoscale dynamical analysis. The discovery of a robust IOD-North East Nigeria teleconnection constitutes a novel empirical finding with direct implications for seasonal rainfall predictability in an already food-insecure region. Keywords: Indian Ocean Dipole, North East Nigeria, teleconnection, rainfall variability, Lake Chad basin.