Temporal Dynamics of Noon-Time Temperature in Selected Cities in Sudan Savanna and Tropical Rainforest Zones of Nigeria

Abstract

Urban centres in Sub-Saharan Africa have been undergoing unprecedented urbanization in the past decades at annual rates of almost 4%; with attendant impacts on the cities’ thermal conditions. This study aimed at characterizing the noon-time maximum temperature of two selected cities each in the Sudan and Tropical Rainforest zones of Nigeria. The study utilized daily ERA Interim (European Reanalysis) grid-based 2 meter above ground daily noontime maximum temperature (°C) data of the European Centre for Medium-range Weather Forecasts (ECMWF) from 1990 to 2019. R Statistical package version 3.6.1 was employed to detect the trend and seasonality in the maximum noon-time temperature of the four cities using non-parametric Mann Kendall trend and seasonal trend tests. The statistical properties of the data were first analyzed by graphical examination of the data, using time plots, and boxplots. Also, the normality test of Shapiro-Wilk (S-W test) was applied. Pettitt test was then employed to test for single change-point detection in the temperature series. The study revealed higher mean temperature values of 27.49°C and 25.56°C respectively for Birnin Kebbi and Kano both in the Sudan, and lower temperature values of 24.08°C and 23.17°C respectively for Ibadan and Owerri located in the Tropical rainforest. The Tau statistics for Kano, Ibadan and Owerri are 0.07084, 0.09848 and 0.09113 and the corresponding p-values are 0.0447, 0.0053 and 0.0098 which are less than 0.05 alpha value; indicating significant trends for the three cities. The results also show significant seasonal increase at 0.05 significant levels in the maximum noon-time temperature series for all the locations. The study recommends urban landscape planning and design for optimization of outdoor thermal comfort and creation of heathier urban environments for the city dwellers.