Investigating Urban Land Use/Land Cover-Surface Temperature-Atmospheric Temperature Nexus

Land use/land cover (LULC)-surface temperature (ST)-atmospheric (air) temperature (AT) nexus is fundamental in the understanding the dynamics of urban climate. Remote sensing, in conjunction with geographic information system (GIS), is used to investigate the relationships between LULC and ST, 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 the Normalized Difference Vegetation Index (NDVI), Normalized Difference Wetness Index (NDWI) and Normalized Difference Built-up Index (NDBI) are chosen to represent the densities of vegetation cover, moisture and built-up structures in the study area. The effects of NDVI, NDWI and NDBI on ST, and ST on 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.