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Home  >  Volume 38

35. Analyzing Chaotic Trends in Rainfall, Solar Radiation and Temperature Records from Some Selected States in Nigeria by E.V. Tikyaa, I.M. Echi and B.C. Isikwue by Volume 38, (November, 2016), pp 249 – 262
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Abstract

This research applies the tools of nonlinear dynamical analysis on meteorological data recorded in some selected states of Nigeria so as to quantify the signatures of chaos and analyze the trend of chaoticity in the data over the last three decades. Investigating the presence of chaos in a dynamical system like weather time series is an important problem that is solved by applying some useful tools such as: observing the weather elements (time series), reconstructing phase space, estimating the Lyapunov spectrum and the largest Lyapunov exponents.A positive value of the Lyapunov exponent indicates the presence of chaos in the system and the larger the value, the lower the predictability of the data set. The data analyzed in this work was obtained from the meteorological department of the International Institute for Tropical Agriculture (IITA) Ibadan, Nigeria and contains daily averages of rainfall and temperature recorded from 1977 to 2010 in six states spread across the country. Rosenstein’s algorithm was deployed in computing the annual Lyapunov exponents for each data set and trend analysis was carried out using Mann-Kendal trend test and Sen’s slope estimator. The results obtained showed that the rainfall, solar radiation and temperature records from the selected states all show strong signatures of chaos, as the largest Lyapunov exponents computed are all positive and their annual Lyapunov exponentvalues showed fluctuating trends which are random and chaotic in nature.The plots from the Sen’s slope estimator show increasing trends in the annual Lyapunov exponents of rainfall and solar radiation and mainly decreasing trends for average temperature. The Mann-Kendal analysis results on the other hand confirmedfrom the Z-tests that the trends in the annual Lyapunov exponents of the three parameters across the six states are insignificant except for solar radiation in Kano. Thusit is insinuated that the phenomena of climate change which is caused by greenhouse gas emissions from human and industrial activities across the country has affected the chaoticity and predictability of the atmosphere over Nigeria by causing random fluctuations in the trend of its predictability and thus creating more uncertainty in the accuracy of prediction of climatic conditions across the country in the nearest future.

Keywords: Chaos, Phase Space Reconstruction, Time Delay, Embedding Dimension, Lyapunov Exponent, Climate Change.

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