Investigation of the spatial distribution of deterministic chaos in some meteorological variables across Nigeria

In this study, the spatial variation of dynamical complexities in selected meteorological variables over Nigeria were investigated. Quantitative tools of nonlinear analysis such as correlation dimension, Lyapunov exponents and approximate entropy were implemented on daily mean values of meteorological variables recorded across Nigeria from 1982-2020. Results obtained from the analysis confirms that there is low-dimensional deterministic chaotic dynamics in the climate across Nigeria as a result of the positive Lyapunov exponent values obtained; with values spatially ranging from 0.00181-0.0591 for precipitation, 0.00696-0.277 for wind speed, 0.00369-0.26 for temperature and 0.00109-0.00698 for all sky radiation. It was observed that the northern part of the country has higher degree of chaos in precipitation and air temperature as the Lyapunov exponents increased latitudinally while the southern part exhibits more chaotic dynamics in wind speed and all-sky radiation as a result of coastal effects. Correlation dimension values for precipitation significantly affirmed nonlinearity with values ranging spatially from 0.106-2.34 (increasing latitudinally from North to South) while wind speed (3.81-4.26), air temperature (3.55-4.25) and all sky radiation (3.59-4.25) also affirmed nonlinearity and low dimensional chaos but showed insignificant spatial trends across the country. Furthermore, precipitation was found to exhibit more steady repetitive pattern in the northern part of the country with entropy values ranging from 0.359-0.837 while wind speed, air temperature and all-sky radiation showed less repetitive patterns along the border locations in the far north and coastal cities in the south with entropy values ranging from 0.703-0.932, 0.724-0.892 and 0.718-0.877 respectively. The irregular trends are attributed to local and external factors such as human anthropogenic activities leading to greenhouse gas emission/global warming, topography of these locations and variations in the position of the Inter-Tropical Discontinuity as a result of different nonlinear resonances emanating from the coupling of the oceans, the atmospheric system and the El Nino/Southern Oscillations (ENSO).