Shifting the urban heat island clock in a megacity: a case study of Hong Kong

Abstract

With increasing levels of urbanization in the near future, understanding the impact of urbanization on urban heat islands (UHIs) is critical to adapting to regional climate and environmental changes. However, our understanding of the UHI effect relies mainly on its intensity or magnitude. The present study evaluates the impact of urbanization on UHI duration changes by comparing three stations with different rates of urbanization, including highly developed and developing urban areas throughout Hong Kong, from 1990-2015. Results show that the 26 year average UHI intensity in highly urbanized regions is much higher than that in developing areas, and the 26 year average of UHI duration is similar. Over the past 25 years, however, UHI duration has increased only in developing urban areas, from 13.59-17.47 hours. Both earlier UHI starting and later UHI ending times concurrently contribute to the UHI effect being experienced for a longer duration. The differences in UHI duration change between the two areas are supported by population and by night light changes from space. Increasing night light, which suggests enhancements in the economic infrastructure, occurred only in the developing urban areas. Our results suggest that changes in UHI duration should be included in an assessment of regional climate change as well as in urban planning in a megacity.

Urban heat islands in Hong Kong: Bonding with atmospheric stability

“…Some studies have characterized the spatial pattern of UHIs in Hong Kong using land surface temperatures retrieved from remote sensing data (Fung et al ., 2009; Liu and Zhang, 2011; Wong et al ., 2016; Tsou et al ., 2017), and others have evaluated the reliability of UHI intensity as an indicator of urban heating (Memon et al ., 2009). Besides the intensity or magnitude of UHIs, the impact of urbanization on changes in UHI duration has been examined (Chen and Jeong, 2018). Urban planning strategies for adaptation to and mitigation of UHIs are of wide interest to the government and researchers in Hong Kong as well (Giridharan et al ., 2007; Ng et al ., 2012; Tan et al ., 2016; Aflaki et al ., 2017; Lin et al ., 2017; Wang and Ng, 2018).…”

Influence of the Mega-Urban Heat Island on Spatial Transfer of Summer Thermal Comfort: Evidence from Tianjin, China

“…Changes in radiation and thermal properties such as thermal conductivity, emissivity, reflectivity, and the thermal capacity of urban surfaces cause great variations in surface energy balance. Consequently, urban temperature is higher than those in peripheral rural areas [5]. More importantly, the UHI effect undergoes spatial change and transfer and has a comprehensive spatial influence on human comfort and health.…”

Determination of Air Urban Heat Island Parameters with High-Precision GPS Data

“…Additionally, satellite data have been used to estimate AUHI in HK [18,19]. Other studies have used data from the meteorological networks provided by the Hong Kong Observatory to study the AUHI [20,21]. In both cases, the weather station in the Hong Kong Observatory's headquarters in Tsim Sha Tsui was considered as an urban station.…”

“…In both cases, the weather station in the Hong Kong Observatory's headquarters in Tsim Sha Tsui was considered as an urban station. However, rural stations have been defined differently; the station in Tsak Yue Wu [20] and the one in Ta Kwu Ling [21] have both been defined as rural. Siu and Hart [20] found that a maximum intensity of 2.5 • C occurs at around 20:00 local time.…”