A Comprehensive Statistical Study on Daytime Surface Urban Heat Island during Summer in Urban Areas, Case Study: Cairo and Its New Towns

Abstract

Surface urban heat island (SUHI) is defined as the elevated land surface temperature (LST) in urban area in comparison with non-urban areas, and it can influence the energy consumption, comfort and health of urban residents. In this study, the existence of daytime SUHI, in Cairo and its new towns during the summer, is investigated using three different approaches; (1) utilization of pre-urbanization observations as LST references; (2) utilization of rural observations as LST references (urban-rural difference); and (3) utilization of the SIUHI (Surface Intra Urban Heat Island) approach. A time series of Landsat TM & ETM+ data (46 images) from 1984 to 2015 was employed in this study for daytime LST calculation during summer. Different statistical hypothesis tests were utilized for the evaluation of LST and SUHI in the case studies. The results demonstrated that there is no significant LST difference between the urban areas studied, and their corresponding built-up areas. In addition, daytime LST in new towns during the summer is 2 K warmer than in Cairo. Utilization of a pre-urbanization observations approach, alongside an evaluation of the long-term trend, demonstrated that there is no daytime SUHI during the summer in the study areas, and construction activities in the study areas do not result in cooling or warming effects. Utilization of the rural observations approach showed that LST is lower in Cairo than its surrounding areas. This demonstrates why the selection of suitable rural references in SUHI studies is an important and complicated task, and how this approach may lead to misinterpretation in desert city areas with significant landscape and surface difference with their most surrounding areas (e.g., Cairo). Results showed that, although SIUHI technique can be representative for the changes of variance of LST in urban areas, it is not able to identify the changes of mean LST in urban areas.

A Review and Insights for Eleven Years of Urban Microclimate Research Towards a New Egyptian ERA of Low Carbon, Comfortable and Energy-Efficient Housing Typologies

“…Therefore, a four stages methodology has been applied in case study in Borg El-Arab (Alexandria, Egypt) to compare the thermal performance of urban spaces that applied urban trees, once modeled empirically and another modeled on a measured LAI and Albedo basis [70]. The measurement experiment applied a LAI2200c plant canopy analyzer [71] and the use of two back to back CMP21 second class high temperature pyranometers as albedometers, [72]. Those four steps can be summarized as following; (1) field measurements of albedo and LAI and observations of the trees geometry; (2) digitizing and recomputing the tree initial measurements; (3) modeling the selected local trees numerically to be added to the simulation tool; and (4) and finally modeling and simulation of the urban site selected to assess trees within its built environment.…”

“…Urban heat islands have been investigated in Cairo from a thermal effect point of view in the work of Hamid et al [72] and it was found that Land Surface Temperature (LST) which is the Surface Urban Heat Island (SUHI) in new towns is 2 K warmer than in Cairo due to the non-uniform distribution of urbanization. Moreover, the study indicates that the selection of suitable rural references in SUHI studies is an important in a desert city with significant landscape and surface difference with their most surrounding areas such as Cairo.…”

Diversification of Land Surface Temperature Change under Urban Landscape Renewal: A Case Study in the Main City of Shenzhen, China

“…The urban heat island (UHI), the best example of anthropogenic climate modification resulting from urbanization, is one of the most severe environmental problems affecting human health and ecosystem functioning [2]. Although there is no doubt that the form and expansion of urban landscape directly increases the threats of UHIs, the quantitative spatiotemporal variations of land surface temperature (LST) under urban landscape transformation are diverse [3][4][5][6]. This diversification could be caused by differences in seasons, hours, climate zones, and urbanization types [7][8][9][10].…”

Capturing urban heat island formation in a subtropical city of China based on Landsat images: implications for sustainable urban development

“…Many studies have researched land surface temperature (LST) variations concerning landscape composition to comprehend the impact of urbanization on urban heat islands (UHIs) Weber et al 2014;Zhang et al 2017b). The urban-rural difference has been discussed extensively (Hjort et al 2016;Taheri Shahraiyni et al 2016;Ünal et al 2019), and the relationship between the impervious surface (IS) and green space (GS) has been explored . These previous studies have clarified that urban regions have higher temperatures than rural regions and that the IS regions have higher temperatures than the GS regions Hjort et al 2016;Taheri Shahraiyni et al 2016).…”