Variability in the Long-Term Trends of Rainfall and Temperature over Southern Nigeria

Abstract

This study investigated the variability in the long-term trends of rainfall and temperature over southern Nigeria. The relationship between the trends of temperature and rainfall was also explored. The results show no significant increasing/decreasing trend in monthly, seasonal and annual rainfall, with a decadal sequence of alternately increasing and decreasing rainfall trend. A significant increasing trend of annual maximum, minimum and mean temperature was detected at the rate of 1.1°C, 1.4°C and 1.2°C / 61 years, respectively, with the highest significant monthly increases observed in February and March. The study identifies two distinct climatological time-periods over southern Nigeria. The first period (1950 – 1980) is characterised by annual mean temperature below the climatological average whilst the second period (1981 – 2010) show a rising annual mean temperature consistently above the climatological average with the exceptions of years 1992 and 1994. Although there was no direct relationship between increasing rainfall and maximum temperature in southern Nigeria, a broad spatial-temporal dependence of rainfall on minimum temperature was observed in the dry season.