Enhanced sensitivity of the urban heat island effect to summer temperatures induced by urban expansion

Abstract

A suitable thermal environment is important for the economy, society and public health in urban areas. However, the understanding of the relationship between the urban heat island (UHI) effect and background temperature (T-UHI) is very limited. In this study, the UHI effect induced by the urbanization of the megacity Beijing was investigated using the weather research and forecasting model. Urban expansion and heatwaves both considerably enhanced the UHI effect over urban areas in summer. The strengthened UHI effect during the heatwave period can be clearly explained by the positive sensitivity of T-UHI. The urban expansion increased the sensitivity of T-UHI from 0.0207°C°C −1 in 2000 to 0.0569°C°C −1 in 2010 in the daytime and from 0.0715°C°C −1 in 2000 to 0.0995°C°C −1 in 2010 at nighttime, thus resulting in a much stronger UHI effect mainly by increasing the difference between the latent heat flux and sensible heat flux. This enhanced sensitivity may exacerbate the urban heat stress in the situation of further urban expansion and background climate warming. Our results suggest that the sensitivity of T-UHI is a meaningful indicator to assess the urban thermal environment change and support the designing of heat mitigation strategies in urban planning.

Response of Urban Heat Stress to Heat Waves in Athens (1960–2017)

“…Finally, the study explored the possible interactions or synergies between HWs and heat stress difference between urban and non-urban sites, in accordance to recent research concerning interactions between HWs and UHIs. According to recent literature, there is evidence of synergistic interactions between UHIs and HWs, resulting in the exacerbation of UHI intensity during extreme heat events [24][25][26][27][28]. According to other studies, bigger or smaller cities respond differently during HWs in regards to UHI modification [29].…”

“…Vulnerability to HWs is expected to increase in urban environments mainly due to population density and the effect of the urban heat island (UHI) that make cities hotter than surrounding non-urban areas [23]. Moreover, recent studies point to synergies between HWs and UHIs leading to exacerbation of the UHI magnitude during HW episodes [24][25][26][27][28]. Bigger cities seem to experience an amplification of UHI during HW episodes compared to smaller cities, even though cities with similar size seem to interact differently with HWs [29].…”

“…Although the studies on HWs or heat stress metrics are numerous worldwide, only limited studies focus on the different response of urban and non-urban sites to HWs. However, even these studies are focused on the interaction between HWs and the magnitude of UHI [24][25][26][27][28][29] while, to our knowledge, the different response of urban and non-urban sites to severe HWs based on heat stress metrics (and not UHI intensity) has not been analyzed so far.…”

The Trend Inconsistency between Land Surface Temperature and Near Surface Air Temperature in Assessing Urban Heat Island Effects

“…Hence, this paper focuses on the temporal stability and consistency between LST and SAT, and has the following objectives: (1) to explore the relationships between LST and SAT in different temperature variables of urban and rural areas; (2) to identify the differences of absolute values and temporal trends of UHI intensities from LST and SAT; (3) to analyze the reasons that result in the UHI discrepancies. The Beijing-Tianjin-Hebei (BTH) urban agglomeration in northern China has been used as the study area because of the significant UHI effects [22] and various terrains. Regional, city and site scales were calculated and analyzed.…”

Assessment of urban heat island in Kathmandu valley (1999-2017)

“…The UHI affects urban quality of life through the impact on human health, ecosystem function and local weather and climate (Wienert and Kuttler, 2005). Therefore, the issue of UHI is being a crucial issue in various disciplines whether they are natural or social sciences because of the multiple implications on climatic system and human welfare (Gao et al, 2019). Remote sensing technology has made possible to monitoring UHI creation of urban areas more efficiently and cost effective due to freely available thermal images (Jeevalakshami et al, 2017) and its application is growing with urbanization process in the world.…”