Browsing by Author "Dada, Babatunde J."

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    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.
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    Tropospheric delay in microwave propagation in Nigeria
    (Arxiv, 2018-11-29) Ogunjo, Samuel; Dada, Babatunde J.; Oluyamo, Sunday; Fuwape, Ibiyinka
    Satellite communication systems suffer from the systematic error of tropospheric delay. Accurate estimation of this delay is essential for communication budget and planning. This study investigates the tropospheric delay in three Nigeria cities: Abuja, Lagos, Port-Harcourt using two different models (Saastominen and Hopfield). Three year atmospheric data for surface pressure, relative humidity and temperature obtained at 5-mins interval were acquired from the Tropospheric Data Acquisition Network (TRODAN) archives. Computed radio refractivity values showed distinct seasonal dependence in Abuja with low and high values during the dry and wet season respectively. The Hopfield model predicts higher hydrostatic delay values than the Saastominen model. In the non-hydrostatic delay, the two models converge to a single values at high temperature. Theorems were proposed with proofs to explain the relationship observed between the two models.