TRENDS AND VARIATIONS OF MONTHLY MEAN MINIMUM AND MAXIMUM TEMPERATURE DATA OVER NIGERIA FOR THE PERIOD 1950-2012. (Published)
The monthly mean maximum and minimum temperature data were analysed with the aim of revealing spatial and temporal pattern of long-term trends in the variables. The study is based on the data collected from Nigeria Meteorological Agency’s network of meteorological stations spread across Nigeria spanning from 1950-2012. A total of 20 meteorological stations spread across Nigeria were used for the analysis. Statistical techniques such as time-series plots, correlation analysis, descriptive statistics and Mann-Kendall’s test were used for the analysis. These analyses were executed using the R programming language, MATLAB and SPSS computer software packages. The results show latitudinal dependence of basic temperature characteristics with the northern part of the country exhibiting higher temperature variability than the south. The Mann-Kendall tests indicate that 17 stations (representing 85%) show significant increasing trends in the minimum temperature at the 0.01 level of significance while 16 stations (representing 80%) show significant increasing trends in the maximum temperature at the 0.01 and 0.05 significance levels. Port Harcourt and Ikeja have greatest trend coefficients among the 20 stations. The minimum temperatures have higher trend coefficients than the maximum temperatures for almost all the stations. The interstation spatial coherence revealed by correlation coefficients indicates that almost all the station’s minimum and maximum temperatures are positively correlated with others at the 0.01 level of significance. The Mann-Kendall’s test results show a general warming trend across the stations.
Keywords: Mann-Kendall, Nigeria, Trends, maximum temperature, minimum temperature, variability