Investigating the urban heat and cool island effects during extreme heat events in high‐density cities: A case study of Hong Kong from 2000 to 2018

Abstract

Urban heat island (UHI) and cool island (UCI) effects are well-known and prevalent in cities worldwide. An increasing trend of extreme heat events has been observed over the last few decades and is expected to continue in the foreseeable future. In this study, warm periods (May to September) of 2000-2018 were examined to acquire a comprehensive understanding of the UHI and UCI characteristics for the case study of Hong Kong, China. Twenty-two weather stations in Hong Kong were classified into four categories, namely urban, urban oasis, suburban, and rural, with reference to the local climate zone (LCZ) scheme, to analyze UHI and UCI phenomena during extreme heat and non-extreme heat situations. One representative type of extreme heat events was considered in this study: three consecutive hot nights with two very hot days in between (2D3N). Results show that both the UHI and UCI effects are exacerbated during extreme heat events. Using the concept of the UHI degree hours (UHIdh) and UCI degree hours (UCIdh), their spatial patterns in Hong Kong during extreme heat and non-extreme heat situations were mapped based on multiple linear regression models. It is found that the predictor variablewindward/leeward index is a significant influential factor of both UHIdh and UCIdh during extreme heat events. The resulting UHIdh and UCIdh maps not only enhance our understanding on the spatial pattern and characteristics of the UHI and UCI during extreme heat events, but could also serve as a Abbreviations: 2D3N, three consecutive HNs with two HDs in between; EH, extreme heat (EH) event; HD, very hot day; HDHN, when both HD and HN happen on the same day; HN, hot night; LCZ, local climate zone; MLR, multiple linear regression; non2D3N, normal summer days without 2D3N events; non-EH, non-extreme heat (non-EH) event; nonHD/HN, normal summer days without any individual HDs, HNs and their combinations; UCI, urban cool island; UCIdh, UCI degree hours; UHI, urban heat island; UHIdh, UHI degree hours.

Spatial and temporal characteristics of near‐surface air temperature across local climate zones in a tropical city

“…An increasing interest in tropical cities is noticeable since the 1990s as summarized in Roth (2007), including cities in Latin America (e.g., Jauregui, 1996; Jauregui, 1997; Gonzalez et al ., 2005), sub‐Saharan Africa (e.g., Adebayo, 1991) or South and Southeast Asia (e.g., Tso, 1996; Deosthali, 2000; Wong and Yu, 2005; Chow and Roth, 2006). The observations reported in these studies, together with more recent studies from Hong Kong, HKSAR (Ren et al ., 2021), various Indian cities (Kotharkar et al ., 2018), Kuala Lumpur, Malaysia (Ramakreshnan et al ., 2019) and Akure and Lagos, Nigeria (Balogun et al ., 2012; Balogun and Balogun, 2014; Ojeh et al ., 2016), show similarities to results from temperate cities. They confirm the well‐known morphology of T a , which is sensitive to building density or land‐use.…”

Spatiotemporal Analysis of Urban Heat Islands and Vegetation Cover Using Emerging Hotspot Analysis in a Humid Subtropical Climate

“…This effect can negatively influence human health (heat-related illnesses and mortality) and the environment (increased energy usage and greenhouse gas emissions) [3]. Understanding the temporal and spatial variations of the heat island effect can thus assist policymakers and urban planners in developing effective mitigation solutions to mitigate its detrimental effects [4].…”