The Impact of Urban Heat Island (UHI) Phenomenon on the Climate of Qatar

Rapid urbanisation can potentially raise the ambient surface temperatures in recently developed built-up areas of large cities due to what is known as the urban heat island (UHI) effect. The increasing temperature trends due to global warming further aggravates the UHI effects. Advanced statistical techniques were used aimed at assessing the UHI effect on Doha city and the extent of such urban contributions to the observed local warming trends. The analysis was initially carried out using the meteorological time series data. The non-parametric Mann-Kendall test was applied on this data to assess the long-term temperature difference trends between Doha and the surrounding non-urban locations. This was followed by spatial assessment using remote sensing data of the factors that are envisaged to contribute to the UHI effect, namely the extent of urban expansion in different locations in Qatar. The unsupervised k-means clustering method was applied for this purpose in order to estimate the areal extent of urban environment in Doha and at other non-urban locations. This was specifically carried out in this study by using the Landsat 5 and 8 images. In addition, the land surface temperatures (LST) were calculated for all the locations considered. Landsat 8 and ASTER images were used for this purpose by implementing the reflectance conversion algorithm. Subsequently, the LST maps were correlated with the urban expansion in order to finally identify the UHI hot spots in Doha city. The main findings of the current study are: (1) The statistical tests indicate that the temperature difference trends between Doha and other non-urban places are generally significantly positive for mean, minimum and maximum temperatures averaged at monthly, seasonal and annual time scales; (2) Image processing results clearly indicate an expanding urban cover (built environment) for Doha in comparison to other places considered; (3) Combined analyses of both temporal and spatial data provide valuable evidence for a significant positive correlation between the urban expansion and the UHI effect.