Browsing by Author "Ogunjo, S. T."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Dynamics of vertical profile of Radio Refractivity in Akure South-Western Nigeria.
    (Proceedings of 2016 Annual Conference of African Geophysical Society, Abidjan, 2016) Ogunjo, S. T.; Fuwape, I. A.; Oluyamo, S. S.; Rabiu, A. B.; Dada, Babatunde J.
    This research investigated fractal and chaotic dynamics in the vertical profile radio refractivity in the atmosphere using Tsallis Entropy, Hurst Exponent and Largest Lyapunov Exponent (LLE). Daily temperature, relative humidity and radio refractivity data obtained from the European Centre for Medium Range Weather Forecasts (ECMWF) Re-Analysis Project at thirty seven (37) different atmospheric pressure level from 1979-2014 were used in this study. The Hurst Exponent parameter obtained, using the method of Detrended Fluctuation Analysis, in the radio refractivity profile studied showed that there is persistence across all levels. Tsallis entropy did not reveal any structure or significant variations from the tropopause to the surface. To determine if any of the radio refractivity is chaotic at any of the studied level, the Largest Lyapunov Exponent (LLE) was computed. Positive values were obtained at all levels for radio refractivity, indicating deterministic chaos in the profile of radio refractivity.
  • Thumbnail Image
    Item
    NONLINEARITY IN RADIO REFRACTIVITY OVER AKURE, SOUTHWESTERN NIGERIA1
    (ook of Proceedings of the 5th Annual Conference of the Nigerian Union of Radio Science, 2013) Ogunjo, S. T.; Ojo, J.S.; Adediji, A.T.; Adedayo, K.D.; Dada, J.B.
    Chaos has found applications in many disciplines including radio communication. It has been applied to secure communication and time series analysis of many parameters. This study investigates chaos in the calculated refractive index over Akure using a two year data obtained from ongoing measurement of some atmospheric parameters by the communication and atmospheric physics research group, FUT, Akure. Chaos in the time series was investigated using phase space reconstruction, time delay, embedding dimension and Lyapunov exponent. Preliminary results shows positive Lyapunov exponent, hence, long term prediction of refractive index is impossible.