EFFECTS OF URBANIZATION ON LAND SURFACE TEMPERATURE IN PARTS OF SUDAN SAVANNA AND RAINFOREST ZONES OF NIGERIA

Abstract

The study aimed at assessing the effects of urbanization on Land Surface Temperature (LST) in four selected cities in Sudan Savanna and Rainforest Ecological Zones of Nigeria. The cities are Ibadan and Owerri in the Rainforest zone, and Kano and Birnin Kebbi in the Sudan Savanna zone, Kano, Owerri and Birnin Kebbi. The study utilized Landsat TM, ETM+ OLI data from the United States Geological Service from the global visualization repository for the years 1990 to 2019, and ERA-Interim (European Reanalysis) grid-based 2 meter above ground daily temperature data from ECMWF repository for the four surveyed cities from 1990 to 2019. To achieve this, the study analyzed LULC change, NDVI, NDBI and LST for the four cities using Idrisi Terrset version 18.21 software and ArcGIS ArcMap 10.8 software. For the ERA-Interim data, R Statistical package software 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 thesis established that built-up areas increased from 312.90 km

(9.19%), 70.32 km 2 (12.94%), 58.48 km 2 (11.85 %) and 14.06 km 2 (1.13%) in Ibadan, Owerri, Kano and Birnin Kebbi respectively in 1990 to 1,039.54 km 2 (30.55%), 209.16 km 2 (38.50%), 216.03 km 2 (43.77%) and 123.03 km 2 (9.85%) in 2019 respectively. This implied a high rate of urbanization process in all the cities, and a concomitant decrease in other land cover types; with a resultant imbalance in the ecosystem of the urban environment. The study also established differences in values of the mean noon-time air temperature; indicating higher temperature values in Birnin Kebbi (27.49°C) and Kano (25.56°C) both in the Sudan, in contrast with lower temperature values of 24.08°C and 23.17°C for Ibadan and Owerri respectively located in the Rainforest. Furthermore, the thesis established a Tau statistics of 0.070, 0.098 and 0.091, and corresponding p-values are 0.045, 0.005 and 0.0098 which are less than 0.05 confidence level for Kano, Ibadan and Owerri respectively; indicating significant rising trends of noon-time temperature in the three cities. Aside the mean LST-NDBI correlation of 0.94, 0.98, 0.96, 0.98 in Ibadan, Owerri, Kano and Birnin Kebbi respectively, the study established an increase in coverage areas of high LST areas from 18.12%, 18.07% and 14.71% respectively in Ibadan, Owerri and Birnin Kebbi respectively in 1990 to 27.00%, 52.12% and 64% in 2019. This implied that as the urban sizes increase in the cities, the coverage area of higher LST increases. The study recommended adequate urban land use planning and initiation of urban greening processes and carbon sequestration as mitigating measures for high LSTs in the cities. 2