Investigating the Relationships between Land Use/Land Cover and Surface Temperature and Air Temperature in Makurdi, Nigeria

The relationships between Land use/land cover (LULC) and surface temperature (ST) and air (atmospheric) temperature (AT) in cities are fundamental in understanding the dynamics of urban heat island (UHI) phenomenon. Remote sensing, in conjunction with Geographic Information System (GIS), is used to investigate the relationships between LULC and ST and AT in Makurdi, North central Nigeria. A total of twelve (12) Landsat TM/ETM+ images are acquired for January, April and June of 1991, 1996, 2001 and 2006 for the study. Air temperature data are collected from two weather stations on dates of the twelve images. Three LULC indices namely Normalized Difference Vegetation Index (NDVI), Normalized Difference Wetness Index (NDWI) and Normalized Difference Built-up Index (NDBI) are used to represent the densities of vegetation cover, moisture and built-up structures, the dominant LULC types in the study area. The relationships between NDVI, NDWI and NDBI and ST and AT are investigated using correlation analysis with test of significant relationships using students' t-test at 95% confidence level. The results show that areas of water, forest, undergrowth/wetland and cultivated land have decreased by 4km2 (19%), 37km2 (28%), 119km2 (32%) and 19km2 (14%) from 1991-2006. Conversely the area of built-up land has increased by 179km2 (130%) during the same period. ST is negatively correlated with NDVI and NDWI but significant correlation occurs only between ST and NDWI for all the 12 images. There is a positive and significant correlation between ST and NDBI for all the 12 images. ST is significantly and positively correlated only with maximum and mean AT. The study concludes that both vegetation cover and moisture diminish ST but the cooling potential of the latter is higher than the former. Built-up structures enhance ST, which in turn enhances AT particularly during daytime.