Abstract
ABSTRACTThe difference between surface and air temperature within a city and its surrounding area is a result of variations in surface cover, thermal capacity, and 3-dimensional geometry. This research has examined and quantified the decreasing daytime land surface temperature (LST) in Erbil, Kurdistan region of Iraq, and the influence of rapid urban expansion on urban heat/cool island effect over a 20 year period. Land-use/land-cover change across this time period is also established using pixel samples. The current study proposes the application of the normalized ratio scale (NRS) to adjust the temperature of images acquired at different dates to the same range. Eleven satellite images acquired by Landsat 4, 5, 7, and 8 during the period 1992–2013 are used to retrieve LST. The results indicate that 55.3 km2 of city land cover changed from bare soil to urban; consequently, the mean LST of the new urbanized area decreased by 2.28°C. The normalized difference vegetation index (NDVI) of Sami Abdul-Rahman (S.A.) Park increased from 0.09 ± 0.01 to 0.32 ± 0.11, resulting in a decrease of the mean LST by 7.29°C. This study shows that the NRS method is appropriate for detecting temperature trends from urbanization using remote-sensing data. It also highlights that urban expansion may lead to a decrease in daytime LST in drylands.
Highlights
The difference between surface and air temperature within a city and its surrounding area is a result of variations in surface cover, thermal capacity, and 3-dimensional geometry (Oke 1981; Robinson Peter and Ann 1999)
In order to understand the characteristics of the new method, LSTNRS method (D) was compared with the non-normalized method (A), rescaling images to the same minimum and maximum in 1992 (B) and NLST (C)
The current study proposes the application of the normalized ratio scale (NRS) to adjust the temperature of images acquired at different date to the same range
Summary
The difference between surface and air temperature within a city and its surrounding area is a result of variations in surface cover, thermal capacity, and 3-dimensional geometry (Oke 1981; Robinson Peter and Ann 1999). Researching land-use/land-cover (LULC) changes in an area helps to assess the amount of man-made modification of the surface and other environmental changes related to human impacts (Xiao and Weng 2007). In an urban climate study, the surface temperature is very significant (Voogt and Oke 2003). Satellite sensors can be used to retrieve and study the surface temperature of urban areas and its spatial patterns (Watson 2012). Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) are widely used to assess the relationship between LST and LULC The correlation between LST and normalized difference vegetation index (NDVI) has been applied extensively (Weng, Lu, and Schubring 2004; Sun and Kafatos 2007; Weng and Lu 2008; Schwarz et al 2012)
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