Abstract
An urban heat island (UHI) is a significant anthropogenic modification of urban land surfaces, and its geospatial pattern can increase the intensity of the heatwave effects. The complex mechanisms and interactivity of the land surface temperature in urban areas are still being examined. The urban–rural gradient analysis serves as a unique natural opportunity to identify and mitigate ecological worsening. Using Landsat Thematic Mapper (TM), Operational Land Imager/Thermal Infrared Sensor (OLI/TIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS), Land Surface Temperature (LST) data in 2000, 2010, and 2019, we examined the spatial difference in daytime and nighttime LST trends along the urban–rural gradient in Greater Cairo, Egypt. Google Earth Engine (GEE) and machine learning techniques were employed to conduct the spatio-temporal analysis. The analysis results revealed that impervious surfaces (ISs) increased significantly from 564.14 km2 in 2000 to 869.35 km2 in 2019 in Greater Cairo. The size, aggregation, and complexity of patches of ISs, green space (GS), and bare land (BL) showed a strong correlation with the mean LST. The average urban–rural difference in mean LST was −3.59 °C in the daytime and 2.33 °C in the nighttime. In the daytime, Greater Cairo displayed the cool island effect, but in the nighttime, it showed the urban heat island effect. We estimated that dynamic human activities based on the urban structure are causing the spatial difference in the LST distribution between the day and night. The urban–rural gradient analysis indicated that this phenomenon became stronger from 2000 to 2019. Considering the drastic changes in the spatial patterns and the density of IS, GS, and BL, urban planners are urged to take immediate steps to mitigate increasing surface UHI; otherwise, urban dwellers might suffer from the severe effects of heatwaves.
Highlights
Urbanization impairs the natural landscape as it produces impervious surfaces
Unlike previous Cairo studies [65,72], we focused on land surface temperatures in both daytime and nighttime along the urban–rural gradient to deepen our understanding of urban dynamism within a day and gather critical information regarding climate change mitigation studies
From 2000 to 2010, the impervious surfaces (ISs) area increased from 564.14 to 698.65 km2 ; and from 2010 to 2019, the IS area increased by 171 km2, with a total gain of 305.21 km2 (Table 2)
Summary
Urbanization impairs the natural landscape as it produces impervious surfaces. Rapid urbanization has become one of the most critical global issues in the 21st century [1,2,3,4].Various socio-environmental problems, including climate change [5,6,7], energy systems [8], deforestation [9], water and air quality [10], and environmental health [11], have been attributed to large regions being urbanized too rapidly and without proper planning.The urban heat island (UHI) phenomenon [12,13,14,15], which refers to higher temperatures in urban areas relative to the surroundings, has been studied in many cities around the world [15,16,17,18,19]. Urbanization impairs the natural landscape as it produces impervious surfaces. Various socio-environmental problems, including climate change [5,6,7], energy systems [8], deforestation [9], water and air quality [10], and environmental health [11], have been attributed to large regions being urbanized too rapidly and without proper planning. The distribution of impervious surfaces covered by cement, asphalt, and concrete raises the land’s radiative surface temperature [20] and changes the humidity of urban areas [21,22]. The rise in heat in urban areas has caused various social problems such as increasing water and energy consumption [23], air pollution [24], discomfort, and Remote Sens.
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