Dynamical Analysis and Spatial Distribution of Field Strength Variability across Nineteen Locations in Nigeria: A Nonlinear Approach for Communication Planning<b></b>

Field Strength Variability (FSV) is an important atmospheric propagation parameter that influences terrestrial and satellite communication performance through signal fading, ducting and multipath effects. This study presents a dynamical analysis and spatial distribution of FSV across nineteen locations in Nigeria using a nonlinear approach based on the Hurst Exponent (HE) and Lyapunov Exponent (LE). The selected locations represent the Sahel/Sudan Savanna, Guinea Savanna and Rainforest/Coastal climatic zones. Daily meteorological data obtained from the NASA Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), covering 1982–2022, were used to compute radio refractivity and derive FSV. The spatial analysis revealed a clear north-to-south variation, with higher regional mean FSV values in the Sahel/Sudan Savanna (8.47 dB), decreasing through the Guinea Savanna (7.23 dB) to the Rainforest/Coastal region (4.81 dB). The nonlinear dynamical analysis showed that HE values ranged from 0.2544 to 0.3850, with all values below 0.5, indicating predominantly anti-persistent behaviour. The LE analysis revealed distinct regional dynamics, with positive values predominantly occurring in the Sahel/Sudan and Guinea Savanna regions, indicating sensitive dependence on initial conditions and chaotic behaviour, whereas predominantly negative values in the Rainforest/Coastal region indicated relatively more stable dynamics. The findings demonstrate that both the magnitude and nonlinear characteristics of FSV are strongly influenced by spatial and climatic variability across Nigeria. This study provides insight into the spatial distribution and dynamical behaviour of FSV in tropical environments and offers useful information for radio propagation assessment, communication planning and the development of region specific propagation strategies.