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<p>Understanding the nonlinear behaviour of tropospheric radio refractivity is essential for improving propagation models and strengthening communication system reliability in tropical environments. This study used a nonlinear approach to examines the spatial and temporal variability of deterministic chaos in radio refractivity across 12 Nigerian locations using daily meteorological data (temperature, pressure, and relative humidity) obtained from NASA’s Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) for the period of 40 years (1982 to 2022). Radio refractivity data were computed from the meteorological parameters and nonlinear dynamics were analysed using recurrence plots (RP), recurrence quantification analysis (RQA), the Hurst exponent (HE) and the Lyapunov exponent (LE). The recurrence plots were characterized as chaotic by the appearance of dense diagonal line structures. Embedding dimension m = 4, time delay <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:\tau\:\)</EquationSource> </InlineEquation> =10, this indicates that radio refractivity is governed by similar underlying nonlinear dynamics which suggests comparable system complexity despite geographical differences. Recurrence threshold <i>e = 0.02</i> was selected using the fixed recurrence rate criterion, high recurrence rates (RR) of 0.11 to 5.36%, Determinism (DET) of 0.01 to 0.03, were obtained. The Hurst exponents ranges from 0.641 to 0.769 (HE &gt; 0.5) consistently exceeded the theoretical reference value of 0.5, confirming persistent long range dependence across all the twelve locations. The Lyapunov exponents were small but positive (0.003446 to 0.006594&#xa0;day⁻¹), signifying weak deterministic chaos and finite predictability horizons of approximately 151 to 290 days. Overall, the results show that tropospheric radio refractivity in the study region is persistent, deterministic, weakly chaotic but strongly controlled by climatic variability. These findings seek to help to provide valuable insights for improving radio propagation modelling and support long term communication system planning in tropical environments.</p>

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Analysis of spatial and temporal variation of deterministic chaos in tropospheric radio refractivity across twelve locations in nigeria using recurrence quantification analysis

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • J. A. Bichi,
  • B. I. Tijjani,
  • E. V. Tikyaa

摘要

Understanding the nonlinear behaviour of tropospheric radio refractivity is essential for improving propagation models and strengthening communication system reliability in tropical environments. This study used a nonlinear approach to examines the spatial and temporal variability of deterministic chaos in radio refractivity across 12 Nigerian locations using daily meteorological data (temperature, pressure, and relative humidity) obtained from NASA’s Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) for the period of 40 years (1982 to 2022). Radio refractivity data were computed from the meteorological parameters and nonlinear dynamics were analysed using recurrence plots (RP), recurrence quantification analysis (RQA), the Hurst exponent (HE) and the Lyapunov exponent (LE). The recurrence plots were characterized as chaotic by the appearance of dense diagonal line structures. Embedding dimension m = 4, time delay \(\:\tau\:\) =10, this indicates that radio refractivity is governed by similar underlying nonlinear dynamics which suggests comparable system complexity despite geographical differences. Recurrence threshold e = 0.02 was selected using the fixed recurrence rate criterion, high recurrence rates (RR) of 0.11 to 5.36%, Determinism (DET) of 0.01 to 0.03, were obtained. The Hurst exponents ranges from 0.641 to 0.769 (HE > 0.5) consistently exceeded the theoretical reference value of 0.5, confirming persistent long range dependence across all the twelve locations. The Lyapunov exponents were small but positive (0.003446 to 0.006594 day⁻¹), signifying weak deterministic chaos and finite predictability horizons of approximately 151 to 290 days. Overall, the results show that tropospheric radio refractivity in the study region is persistent, deterministic, weakly chaotic but strongly controlled by climatic variability. These findings seek to help to provide valuable insights for improving radio propagation modelling and support long term communication system planning in tropical environments.