Temporal and scale-dependent associations of Lagos rainfall with Solar and Geomagnetic activity (1995-2024)

Abstract

This study investigated the non-stationary relationships between rainfall variability and solar-geomagnetic activity over Lagos, Nigeria, during 1995-2024, using monthly rainfall, F10.7 solar radio flux, and geomagnetic aa-index data. Deseasonalised anomalies were analysed using 60- and 120-month rolling Spearman correlations, AR(1) surrogate significance tests, false discovery rate (FDR) correction, and Morlet wavelet coherence. Rainfall-F10.7 correlations exhibited significant temporal variability, with maximum absolute coefficients of 0.482 and 0.355 for the respective windows. Both timescales yielded globally significant associations ( and , respectively), although only the 120-month analysis identified FDR-significant windows, predominantly around 2002-2004. Conversely, rainfall-aa correlations were weaker and statistically insignificant at both timescales. Wavelet coherence revealed intermittent, pointwise significant rainfall-F10.7 associations, particularly at 18-26-month and 40-55-month periods, alongside localised rainfall-aa coherence at selected timescales. These findings demonstrate that solar radio flux exhibits a more statistically robust, but temporally variable, association with Lagos rainfall than geomagnetic activity. The results underscore the importance of time-resolved statistical approaches in solar-terrestrial climate investigations while supporting a cautious interpretation of non-stationary associations rather than causal solar control of Lagos rainfall.