Measuring Edinburgh’s Surface Urban Heat Island
Mackinnon, Kerr A H
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This project investigated Edinburgh’s surface urban heat island (SUHI) in relation to land cover and land use. Thermal channels of Landsat TM, Landsat ETM+ and ASTER imagery captured between 1999 and 2011 provide land surface temperatures (LST). SUHI magnitudes over different surface classifications are contrasted diurnally and seasonally. The cause is primarily attributed to solar radiation and the thermal properties of objects it reaches. Urban heat island (UHI) magnitudes and differences between surfaces types are reduced during periods of low solar elevation. Nocturnal and winter SUHIs are shown to have lower magnitudes than that of summertime. If solar radiation is present, larger differences between impervious and non-impervious surfaces are observed. Winter imagery during low solar elevation presented shows no discernible SUHI and no correlation with vegetation. From this it was inferred that anthropogenic warming throughout Edinburgh has a limited effect on the city’s temperature budget. However this result is suggested with caution and demands investigation at higher resolutions. A more gradual nocturnal SUHI was observed, but it remained unclear if any proportion was caused by anthropogenic activity. Compared to other cities where similar analysis has been performed, Edinburgh exhibits a relatively smaller SUHI even during summer. The strength of relationship between Normalised Difference Vegetation Index (NDVI) and LST has been shown to vary with season, whereby stronger correlations are observed during summer. The potential cooling effect of green spaces throughout cities is highlighted. As is the NDVI’s limited to accurately represent vegetation within urban areas.