Remote Sensing and Gis Approach for Estimation of Land Surface Temperature to Examine Urban Heat Island Effect on A City Scale; the Case of Hawassa City, Ethiopia
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Date
2018-05-04
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Addis Ababa University
Abstract
Estimation of Land Surface Temperature (LST) in a city scale is essential for various applications, especially for examining the Urban Heat Island (UHI) effect caused by different factors and identify the relationship of LU/LC types with LST. The integration of interpreted results obtained from Landsat 8 TIRS and MODIS night time data are helpful to identify the major causes for the spatial variation of LST. This helps to examine the heat island effect caused by the geological setting of an area located within the rift zones. Landsat 8 TIRS band 10 data was used to estimate LST of the area. An algorithm that was prepared for Landsat 8 band 10 were used by taking the NDVI method for the estimation of emissivity. The LU/LC maps of the area were prepared with better accuracy using on screen classification technique by identifying 18 different classes that have strong relation with the spatial variation of LST. The UGC types were identified and mapped by integrating computer aided and on-screen classification method using sentinel-2A data. The derived LST showed that the surface temperature of the city ranges from 20.6 to 41.30C and the minimum temperature of the area was observed within the lake and the surrounding areas such as the wetland. The maximum temperature was registered on the scattered and small hills (Tabor Ridge) and areas that are used for mining and some parts of bare lands including industrial park of the city. The spatial variation of LST in the city is the result of four (4) major factors namely: 1) geological setting (volcanic lava domes) and mining areas, 2) human induced activities, 3) the LU/LC type, 4) the nature of the rock (volcanic ash), for their immediate response as a result of absorbance of incident energy from the sun. The mapping of UGC for Hawassa city in detail was found to be good, though mapping and validation of smaller and scattered tree covers were difficult. Increasing of evergreen tree cover and rehabilitation of existing mining areas are among the recommended strategy to mitigate the UHI effects in the city. For future studies in areas that are susceptible to natural heat sources, the satellite data should have high spatial resolution and derived from multiple sensors and satellites that can provide better tools to understand the UHI effect considering the geological setting of the area.
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Keywords
Hawassa, LST, TIRS, Remote Sensing, Rift, Uhis