Diurnal Patterns of Fair-Weather Atmospheric Electric Field in Nigeria: Deviation from Global Standards

Abstract

The first continuous measurements of fair-weather atmospheric electric field in Nigeria reveal distinctive diurnal patterns that fundamentally challenge conventional assumptions about atmospheric electrical behaviour in tropical regions. While the global electric circuit is traditionally characterized by the Carnegie curve derived from maritime measurements, the influence of regional aerosol loading on atmospheric electrical patterns in dust-affected tropical environments remains poorly understood. This study aims to establish the first comprehensive atmospheric electrical climatology for Nigeria and quantify the impact of local aerosol influences on diurnal electric field patterns. Based on 418 fair-weather days over 30 months at Lokoja (7°49'N, 6°44'E), the atmospheric electric field exhibits a pronounced double-peak structure with morning (08:30 LT) and evening (19:45 LT) maxima, reaching amplitudes 2.8 times the daily mean during the dry season. This pattern contrasts sharply with the classical Carnegie curve, showing a weakly negative correlation (r = -0.42) that indicates dominant local aerosol influences over global electric circuit signals. Harmonic analysis reveals that 87% of temporal variance is captured by the first three harmonics, with the 12-hour semidiurnal component contributing 24%—substantially higher than the <5% typical of maritime stations. The diurnal amplitude factor varies systematically from 3.4 during Harmattan dust periods to 1.8 during the wet season, directly tracking regional aerosol loading patterns. These findings establish the first baseline atmospheric electrical climatology for Nigeria and demonstrate the necessity of developing region-specific standards for atmospheric electricity research in dust-affected tropical environments. The results have significant implications for global electric circuit modelling and highlight West Africa's unique role in continental atmospheric electrical processes.