Temporal Variability of the Intertropical Discontinuity and Its Relationship with Atmospheric Pressure and Precipitation in Lagos, Nigeria (2015-2024)

Abstract

This study investigated the temporal variability of the Intertropical Discontinuity (ITD) and its relationship with atmospheric pressure and rainfall over Lagos, Nigeria, using 120 monthly observations spanning 2015–2024. Monthly climatology, autocorrelation, cross-correlation, Granger causality and wavelet coherence analyses were employed to examine seasonal variability, temporal relationships and predictive coupling. Results revealed pronounced ITD migration from 6.70°N in January to 20.41°N in August, while atmospheric pressure peaked at 1010.9 hPa in July. Rainfall exhibited a bimodal distribution, with maxima of 285.16 mm in June and 248.66 mm in September, separated by an August minimum of 64.27 mm. ITD-pressure wavelet coherence reached 0.978 at 1.076 years but declined to 0.355 following deseasonalisation. Similarly, ITD-rainfall coherence approached 0.97 annually but weakened substantially after seasonal adjustment, retaining intermittent subannual coherence. Granger causality revealed no significant bidirectional ITD-pressure predictive relationship at 1-6-month lags (p > 0.05). The study distinguishes strong seasonal synchronisation from weaker anomaly coupling, demonstrating that ITD migration characterises monsoon seasonality but cannot independently explain coastal rainfall variability, thereby providing new insights into Lagos atmospheric dynamics and climate variability.