Spatial characteristics of urban heat island intensity across different land use types in Ibadan Metropolis, Nigeria

Abstract

The effect of urban heat island intensity (UHII) is closely monitored in most developed countries of the world, unlike in developing countries where increased UHI effect is still a secondary concern. This study examined the spatial pattern of temperature as a precursor to describing and explaining the urban heat island (UHI) effect, and analysed the spatial pattern of UHI intensities across different land use types and assessed the variations in the magnitude of UHI across the land use types and residential densities in Ibadan metropolis. Maximum and minimum temperatures obtained were sourced from six weather stations from 1993-2012. Eighteen point locations were randomly selected by dividing the study area into 40 grid cells of 1 km × 1 km to enable a proper extraction of climatic parameters and ensure adequate spatial coverage across different land use types. Also, a supervised classification of Landsat thermal image was done to analyse the land use dynamics of Ibadan over the period 1984- 2013.The result of the findings on the general pattern of temperature showed that there are spatial variations in  temperature, with a higher trend during the dry season while the urban heat island effects were found to be more noticeable in densely built-up areas and at commercial centres. In terms of land use component analysis, it was observed that the built-up areas had increased from between 6.36km² in 1984 to 46.944km² in 2013, at an annual rate of 2.59%. Also, the result of ANOVA showed a significant difference in UHI intensity across different land use types (F_1,46=8.068, p ≥ 0.05). The study concluded that UHII varies significantly over a spatial scale. To have a sustainable city, this study therefore recommends the adoption of the decentralisation of commercial activities and the green-city approach.

Keywords: Urban Heat Island Intensity (UHII), Urban climate, Remote sensing, Land use